Juan A. Embil, MD, FRCP(C) John M. Embil, BSc Gastointestinal Parasitic Infections SUMMARY RESUME This article surveys the most important Cet article passe en revue les principaux parasites gastro- gastrointestinal parasites that affect humans. intestinaux qui affectent les humains. L'auteur en examine brievement les modes d'infestation, la pathologie, The modes of acquisition, pathology, l1'pid6miologie, le diagnostic et le traitement. Les parasites epidemiology, diagnosis, and treatment are all gastro-intestinaux occupent une place de plus en plus briefly examined. Gastrointestinal parasites importante dans le diagnostic diffrentiel de la maladie have become increasingly important in the gastro-intestinale et ce, A cause d'un certain nombre de differential diagnosis of gastrointestinal circonstances. Celles-ci incluent: deplacements de plus en plus nombreux vers les pays en voie de developpement; disease, as a result of a number of augmentation, pour une raison ou pour une autre, du circumstances. These circumstances include: nombre d'individus dont l'immunite est compromise; plus increasing travel to developing countries; grande consommation de mets ethniques crus ou increased numbers, for one reason or another, partiellement cuits; surpopulation dans les garderies; of immunocompromised individuals; increased accroissement des immigrants en provenance de pays en consumption of raw or partially cooked ethnic voie de developpement; et une endemie d'individus dont delicacies; more crowding in day-care centres; les pratiques sont contraires A l'hygiene ou A la salubrite. increased immigration from developing countries; and an endemic pocket of individuals with certain unhygienic or unsanitary practices. (Can Fam Physician 1988; 34:619-626.) Key words: gastrointestinal parasites; nematode, cestode, trematode and protozoan infections.

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Dr. J.A. Embil is a professor of individual. For the attending physi- of gastrointestinal parasitic infections Microbiology, and Community Health cian, they may also present diagnostic has been increasing as a result of a and Epidemiology, and an associate conundrums. Infections that are symp- number of circumstances: increased professor of Pediatrics at Dalhousie tomatic usually mimic other diseases international travel3 to under- University and the Izaak Walton and thus can rarely be diagnosed on developed and developing countries; Killam Hospital for Children, clinical grounds alone. Unfortunately, growing numbers of immu- Halifax. Mr. J.M. Embil is a third- laboratory identification ofthe offend- nocompromised people whose condi- year medical student at Dalhousie ing parasite, which is usually accom- tion has come about either University. Requests for reprints to: plished by a technologists's subjective therapeutically, because of transplant Dr. J.A. Embil, Infection and assessment of the patient's stool sam- operations and other chemo- Immunology Research Laboratory, ple,' is the only way to determine the therapeutic interventions, or intrin- Izaak Walton Killam Hospital for most appropriate mode oftherapy. sically, as in the case of persons with Children, 5850 University Avenue, Parasitic infections can be acquired acquired immune deficiency syn- Halifax, N.S. B3J 3G9 in both tropical and temperate en- drome (AIDS);4 increased consumption vironments. The incidence depends on of raw or partially cooked ethnic deli- GASTROINTESTINAL PARA- climate, sanitation, and socio- cacies5-7 and organically grown pro- IJSITIC infections are often disturb- economic conditions.2 duce; more crowding in day-care cen- ing and uncomfortable for the afflicted During the past few years, awareness tres8 and nursing homes; increased

CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 619 immigration from developing coun- soil before they become infective.9 in a single dose of 100 mg, repeated tries; and endemic pockets of indi- * Pathology and symptoms: Intes- after two weeks. This treatment is ap- viduals with certain unhygienic or un- tinal manifestations include obstruc- propriate for adults and children over sanitary practices.2 tion, vague abdominal discomfort, di- two years ofage.'2 Although the treatment of bacterial arrhea, and of protein, infections is facilitated by an ever- fat, and vitamins.'0 The adult worms Trichuris trichiura (whipworm) growing armamentarium of chemo- may also migrate, penetrating to such * Disease: Trichuriasis. therapeutic agents, the treatment of unusual sites as the liver, gall bladder, * Mode ofacquisition: This parasite parasitic infections depends heavily on pancreas, peritoneal cavity, , is acquired by a mechanism similar to just a few agents. We have made every and pharynx. Severe damage to the pa- that described for Ascaris effort to include, in the material that tient is the usual result of this lumbricoides.'3 follows, the most up-to-date treatment migration.9 * Pathology and symptoms: Patients regimens and dosages; however, as * Epidemiology: While this parasite with light parasite loads generally have medicine is a dynamic field in which is cosmopolitan, it is most frequently asymptomatic infections; patients with changes are constantly evolving, every associated with poor sanitation and the very heavy chronic infections, physician, before administering any use of human feces for fertilizing however, present with anemia, abdom- therapeutic agent, should consult the crops." inal pain, and ; directions on the drugpackage to verify * Diagnosis: Diagnosis is established may develop in children. dosages, dose intervals, contraindica- by finding the characteristic ova in a . Epidemiology: The incidence of tions, and recommendations for use. stool specimen. this infection is relatively low in tem- The four major classes of gastroin- * Treatment: Treatment consists of perate zones; in tropical areas preva- testinal parasites-nematodes, ces- mebendazole, 100 mg bid x 3 d; or lence is very high.9 todes, trematodes and protozoans- pyrantel pamoate at a single dose of 11 * Diagnosis: Diagnosis is established contain organisms that are unique in mg/kg to a maximum of 1.0 g; or byfinding in the stool the characteristic the structure, the morphology, and the piperazine citrate, 75 mg/kg (max. 3.5 barrel-shaped eggs with bipolar plugs. gastrointestinal and systemic man- g)/d x 2 d. These therapies are recom- * Treatment: Mebendazole, 100 mg ifestations they produce. mended for adults and children over bid x 3 dis useful fortreatingadults and two years ofage.'2 children over two years ofage. The Nematodes Enterobius vermicularis (pinworm) Ancylostoma duodenale and Necator Nematodes are non-segmented * Disease: Enterobiasis. americanus (Old and New World round worms which are, for the most * Mode ofacquisition: This parasite hookworms) part, free-living inhabitants ofsoil and is acquired by ingestion of embryo- * Disease: Ancylostomiasis. fresh water. The parasitic species of nated eggs or by inhalation ofdust con- * Mode ofacquisition: Hosts acquire nematodes, however, have generally taminated with eggs. The female para- this parasite by walking barefoot over developed a complex dependence on a site travels at night to the host's anus contaminated soil, where the infective particular host or group ofhosts with- and perianal areas to lay her eggs, caus- filariform larvae penetrate the intact out which they would be unable to sur- ing pruritus. The eggs thus introduced skin. Once through the skin, the larvae vive.9 The most commonly encoun- hatch in the and mature in migrate through the circulation system tered intestinal nematodes infecting the .'3 Hosts who scratch and, after arriving at the lungs, burst humans are discussed below. the pruritic area and then, un- through the alveoli and ascend the thinkingly, put their hands into their pharynx, where they are coughed out mouth may reintroduce the eggs. or swallowed. When those swallowed Ascaris lumbricoides (roundworm) * Pathology and symptoms: Pin- reach the , they attach to * Disease: Ascariasis. worm infections are frequently the mucosa and mature into adults. * Mode of acquisition: These para- asymptomatic, but ifthe worm load is Eggs are passed in the feces and mature sites are acquired through ingestion of extreme, obstruction or perforation of in the soil.9 feces-contaminated food or water con- the intestine may occur. It has been * Pathology and symptoms: Patients taining embryonated eggs carrying the suggested that enterobiasis may cause experience gastrointestinal blood loss fully developed second-stage larvae. cystitis in young females.'4 because the parasites feed on the villus Larvae emerge in the host's duo- * Epidemiology: E. vermicularis has tissues. However, iron-deficiency ane- denum, enter the portal system into the the widest geographic distribution of mia and hypoalbuminemia are seen liver, travel through the venous system any helminth, crossing all social and only in patients with heavy parasite into the lungs (producing a transient economic barriers.'5 loads.'0 pneumonia-like syndrome), penetrate * Diagnosis: Enterobiasis is readily o Epidemiology: Necator americanus through the alveoli, and ascend the diagnosed by a finding of female is common not only in America but bronchial tree to the pharynx, where worms or characteric eggs (flat on one also in West Africa, Ceylon, the Pacific they may be coughed out or swallowed. side and rounded on the other) on anal Islands, and Malaya. Ninety percent of Those that are swallowed reach the je- swab. the ancylostomas in the tropics are of junum, where they develop into adult * Treatment: Treatment may consist this species. Ancylostoma duodenale is worms. The female produces eggs of pyrantel pamoate given in a single widespread in tropical and subtropical which are passed in the feces. The eggs dose of 11 mg/kg (max. 1 g), repeated areas.'3 require two weeks incubation in the after two weeks; or mebendazole given * Diagnosis: Diagnosis is established 620 CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 by the finding of characteristic ova in tric juices liberate the encysted larvae, now being seen in North America.'6 the host's stool samples. It is impossi- which then mature and mate. The * Diagnosis: Because infected pa- ble to distinguish between the eggs of adult female liberates live larvae; the tients are often in distress, endoscopy, the two parasites. larvae enter the host's lymphatic ves- laparatomy, or surgery have been per- * Treatment: Treatment consists of sels and from there gain access to the formed to determine the cause. Fre- mebendazole, 100 mg bid x 3 d, or general circulation. The newborn lar- quently the parasite can be seen in the pyrantel pamoate, 11 mg/kg once (max. vae then penetrate and encyst in mucosa on endoscopy and can there- 1 g). These doses are suitable for adults striated muscle.'6 forebe extracted, relieving thepatient's and children over two years of age.'2 * Pathology andsymptoms: Little pa- symptoms.19 thology occurs in the small intestine, * Treatment: In mild asymptomatic Strongyloides stercoralis (small although some nausea and vomiting cases, the parasite is expelled from the intestinal roundworm) have been reported. Approximately body by coughing, vomiting or defeca- * Disease: Strongyloidiasis. two weeks afteringestion, when the lar- tion; in more severe cases, however, * Mode ofacquisition: This parasite vae are invading the muscle tissue, in- surgical removal has been undertaken. is acquired through a mechanism sim- tense inflammation of muscle tissue Thiabendazole, 25 mg/kg bid x 3 d ilar to that used by the hookworm, and myalgias occur. Periorbital edema (max. 3 g/day) for adults and 25 mg/kg whereby the filariform larvae penetrate is also frequently noted.'7 x 3 d for children over two years ofage unbroken skin. The ova hatch in the * Epidemiology: This parasite is is adequate treatment, however, ifsur- submucosa ofthe host's gut and liber- found world wide. gical intervention is not necessary to ate the rhabditiform larvae. These lar- * Diagnosis: Definitive diagnosis re- relieve obstruction.'2 vae can either enter the gut lumen and quires a muscle biopsy, preferably The Cestodes be passed in the feces, later undergoing from the deltoid, but serological tech- metamorphosis that produces fil- niques such as counter immu- Cestodes, or "tapeworms", have flat ariform larvae in the soil, or they can noelectrophoresis, bentonite floccula- segmented bodies with no gut or body undergo metamorphosis in the gut. In tion tests, latex agglutination tests, and cavity. As a result, they must absorb all the latter instance the filariform larvae indirect immunofluorescence can help nutrients predigested from the host. will penetrate the gut directly, without to establish a presumptive diagnosis. A The segments ofcestodes are the scolex undergoing the soil phase.'6 detailed dietary history is also (head), which is used for attachment to essential.9 the host's intestinal wall, and the pro- * Pathology andsymptoms: The pro- * Treatment: No specific treatment glottids (reproductive and absorptive cess of internal autoinfection can lead exists, as once the parasite is encysted, portions), which are shed when gravid. to an overwhelming number of para- it is protected against eradication. Dur- All members ofthis class are parasitic, sites. This phenomenon is often seen in ing the acute phase, however, pred- lacking a free-living adult stage.'3 They malnourished or immu- nisone may reduce inflammation, inhabit the intestinal lumen ofhumans nocompromised hosts with AIDS, along with eitherthiabendazole 25 mg/ and various other vertebrate hosts. leukemias or lymphomas. Systemic kg bid x 5 d (max. 3 g/d) for adults and Tapeworm infections occur less fre- Gram-negative sepsis and all ofits se- children, or mebendazole 200-400 mg quently than roundworm infections quelae may develop in these patients.16 tid x 3 d then 400-500 mg tid x 10 d for and are less pathogenic.20 A variety of An intense inflammatory process in adults and children. tapeworms exist, some of which are the lamina propria may also occur. more clinically relevant than others; * Epidemiology: Although this para- Anisakis marina (cod or herring the former group will be discussed site is distributed world wide, it is more worms) here. prevalent in tropical and subtropical * Disease: Anisakiasis. areas.'6 * Mode ofacquisition: This parasite Diphyllobothrium latum (fish * Diagnosis: The finding of rhab- is acquired by ingestion ofraw, lightly tapeworm) ditiform and, occasionally, filariform salted or pickled, or inadequately * Disease: Diphyllobothriasis, both- larvae in fresh stools establishes the cooked saltwater fish harbouring the riocephaliasis, dibothriocephalus diagnosis. Duodenal aspiration will oc- infective larvae. anemia. casionally reveal larvae when the feces * Pathology and symptoms: Once in * Mode of acquisition: These para- remain consistently negative, and the the stomach or small intestine, the sites are acquired through consump- string-capsule diagnostic method (En- larva begins to burrow through the tion of improperly prepared contami- terotest) gives good results. mucosa. The patient may be nated freshwater fish, usually pike or * Treatment: Thiabendazole, 25 mg/ asymptomatic or may complain ofup- perch but also salmon.5 The tape- kg bid (max. 3 g/d) x 2 d, is recom- per-abdominal pain, suggesting either worm's larvae, which are embedded in mended both for adults and for child- a peptic ulcer or gastric carcinoma. In the tissue of contaminated fish, de- ren over two years ofage. some patients, obstruction, appen- velop to the adult stage in the small dicitis, , and regional en- intestine ofhumans, bears, foxes, dogs, Trichinella spiralis teritis have been suspected.'8 and any other fish-eating mammals. * Disease: Trichinosis. * Epidemiology: This parasite has so Once they are mature, reproduction * Mode ofacquisition: This parasite far been found most commonly in occurs, and gravid proglottids are is acquired by ingestion of larvae en- Japan and Europe (Finland, Den- passed into the host's colon, where they cysted in raw or undercooked meats, mark). With the growing popularity of break, releasing unembryonated eggs especially pork, bear,7 and walrus. Gas- raw seafood, however, anisakiasis is into the stool.9 These proglottids make CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 621 their way to a supply of fresh water. the recovery and examination of the household pets. Foxes andjackals may The larvae hatch in the water and gravid proglottids (which have 15-20 alsobeinfectedwithD. caninum. Fleas embed themselves in the fish muscle. If uterine branches on each side of the act as an intermediate host, ingesting fish is to be eaten raw, it should first be uterine stem) from the patient's stool the D. caninum eggs. The larvae de- cured adequately in salt or frozen.5 or perineal area. Recovery and exam- velop in the flea, a human accidentally * Pathology and symptoms: Within ination ofa scolex possessing a sucker ingests the flea, and the larvae are re- one to three weeks ofingesting the in- and not hooks is also diagnostic of T. leased in the human's gut. Gravid pro- fected fish, the host may complain of saginata.'3 glottids release the eggs into the feces, general gastrointestinal upset, heart- * Treatment: Treatment is the same which are then shed into the environ- burn, vomiting, diarrhea, nausea, and as for the D. latum.'2 ment, where the flea again ingests the weight loss.' In severe cases, the para- eggs. Infection with thiscestode is often site deprives the host of vitamin B12, Taenia solium (pork wotm) asymptomatic ormayproduce abdom- causing pernicious anemia. * Disease: Taenasis, pork tapeworm inal pain and diarrhea. Diagnosis de- * Diagnosis: Finding the charac- infection. pends on microscopic examination of teristic operculated eggs in the stool * Mode ofacquisition: This parasite stool samples and the finding of the establishes the diagnosis. is acquired through ingestion ofinade- characteristic sac of eggs and proglot- * Epidemiology: The incidence of quately cooked pork infected with the tids, which are longer than they are this parasite is high in Scandinavia, larvae. Its cycle is identical to that of wide. Treatment is the same as that for Finland, and Alaska, and in Canada the T. saginata, except that the pig is D. latum. from the St. Lawrence River to the Pa- the intermediate host. Humans may cific Coast and throughout the Mac- also serve as an intermediate host if Hymenolepsis nana (dwarftapeworm) kenzie River watershed.2' they ingest an egg instead of a larva. and H. diminuta * Treatment: Niclosamide* (given in The eggs can mature, yielding larvae These parasites involve rodents and tablets which must be chewed thor- which penetrate the gut wall and can be insects in their life cycle. Humans are oughly) is an effective treatment. carried hematogenously to striated infected through ingestion ofthe inter- Adults should be prescribed a single muscles, heart, brain, and otherorgans, mediate invertebrate host. Both these dose of2 g. Children weighing 11-34 kg where they can encyst.'6 cestodes are found world wide. A H. may be given a single dose of 1 g, and * Pathology: The symptoms depend nana infection may cause no symp- children weighing more than 34 kg, a on the site ofinfection. Ifthe infection toms or abdominal pain, diarrhea, and single dose of1.5 g. An alternative med- is purely gastrointestinal, symptoms anorexia; most H. diminuta infections ication is praziquantel*, ofwhich a sin- include nausea, vomiting, diarrhea, are asymptomatic or cause slight gas- gle dose of 10-20 mg/kg is recom- and ; if the cerebral sub- trointestinal problems. H. nana and H. mended forboth adults and children.12 stance is involved, epilepsy may diminuta infections are diagnosed by Taenia saginata (beeftapeworm) occur.'6 means of the characteristic embryo- * Epidemiology: This parasitic infec- nated eggs. If proglottids are found in * Disease: Taenasis. tion occurs in pork-consuming the patient's stool, the eggs are ex- * Mode ofacquisition: Hosts acquire countries. tracted and examined. The treatments this parasite by ingestion of raw, rare, * Diagnosis: Diagnosis is established ofchoice for H. nana are niclosamide or inadequately cooked beef infected by detection in the patient's stool of as per D. latum for 4-5 days** or prazi- with the larvae of T. saginata. The lar- gravid proglottids (which have fewer quantel,* a single 25 mg/kg dose for vae are released from the muscle in the than 13 lateral uterine branches at each adults and children.'2 H. diminuta is host's stomach, and the parasites ma- side ofthe uterine stem) and identifica- treated in the same manner as D. ture in the small intestine. Reproduc- tion, after treatment, of a scolex with latum.20 tion yields gravid proglottids, which four suckers and a crown ofhooks. De- are passed in the feces. Embryonated tection and examination ofthe eggs are The Trematodes eggs are next ingested by the cattle, and unreliable procedures as a basis ofdiag- larvae then migrate to tissues.9 Trematodes or "flukes" belong to nosis, as these eggs are similar to those the same phylum (Platyhelminthes; * Pathology andsymptoms: The host of other members of the Taenia is frequently asymptomatic but may flatworms) as the cestodes.13 Both have family.9 flat bodies and no body cavity; they complain of epigastric fullness and * Treatment: Treatment for this in- pain, vertigo, nausea and di- may or may not have a gut. They differ vomiting, fection is the same as that for D. in that trematodes have unsegmented arrhea, and loss ofappetite progressing latum.'2 to frank malnutrition.'6 bodies that are leaf-like or cylindrical. All flukes are obligate parasites, and * Epidemiology: Countries in which Other cestodes beef eating is most common have the male and female parasites are needed highest incidence ofinfection.'3 Although the cestodes described be- for sexual reproduction, whereas the * Diagnosis: Unfortunately, diag- low are distributed world wide, they cestodes are hermaphroditic.9 There nosis cannot be made on examination are seen less frequently in North Amer- are a variety of trematodes, but only ofova collected from stool because the ica than in some other countries. those causing direct gastrointestinal eggs ofthis parasite cannot be differen- symptoms will be considered here. tiated from those ofother members of Diphylidium caninum (dog tapeworm) the Taenia family (T. solium, Echi- Children often acquire this common Clonorchis sinesis (Chinese liver fluke) nococcus granulosus and E. multi- parasite of dogs and cats because of * Disease: Clonorchiasis. ocularis). Thus, diagnosis is based on their close association with these * Mode ofacquisition: This parasite 622 CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 is acquired through ingestion ofraw or vomiting, partial ortotal obstruction of The Protozoans inadequately cooked fish carrying the the , and jaundice. metacercariae in their flesh. Larvae * Epidemiology: F. hepatica is com- Protozoan parasites are unicellular hatch in the small intestine and mi- monly found in herbivores in South free-livingorganisms which have a cos- grate to the where the parasite America, Africa, Europe, China, and mopolitan distribution, and which in- matures and lives.9 Eggs are passed the Southeastern United States.9 fectboth vertebrates and invertebrates. into the bile duct, and eventually exit * Diagnosis: To date, diagnosis de- Unlike the nematodes, cestodes, and the host in the feces. Eggs hatch in fresh pends on microscopic identification of trematodes, the protozoans can multi- water, and the resulting miracidia pen- eggs in the host's stools, although ply rapidly within the host, yielding etrate the intermediate host (i.e., snails serological tests are currently being large numbers of progeny.'3 The class of the genus Bulimus'3), where they developed.'3 contains a varied group of mature to cercariae which encyst in * Treatment: Bithonol**, 30-50 mg/ members, ranging from those that freshwater fish, yielding the metacer- kg on alternate days x 10-15 doses is cause gastrointestinal symptoms to cariae that are consumed by humans. one method of treatment; the alter- those that produce African sleeping most com- * Pathologyandsymptoms: Infection native medication is praziquantel*, 25 sickness. Those protozoans causes , liver ab- mg/kg tid x 5-8 days. Both regimens monly associated with gastrointestinal scesses, biliary tract obstruction, ab- are the same for adults and children. manifestations are as follows. dominal pain, and jaundice.22 Clonorchis infection and cholangicar- Fasciolopsis buski (intestinal fluke) Giardia lamblia cinoma and have been as- * Disease: Fascioliasis. * Disease: (beaver fever). sociated,22 although some researchers * Mode of acquisition: Infection oc- * Modeofacquisition: Infection is ac- believe that clonorchiasis produces no curs through ingestion ofthe metacer- quired by ingestion ofGiardia lamblia significant problems.22'23 cariae which are encysted on vegeta- cysts (the infective stage). * Epidemiology: C. sinensis infec- tion growing in fresh water or on the Trophozoites (the motile forms which tions are endemic in Korea, Japan, shores of bodies of fresh water. Most infects humans) encyst in the host's Vietnam, Taiwan, and China. Al- commonly the infective vegetation small intestine, where they live on the thoughthese parasites are not normally consists of water chestnuts and bam- surface of the intestinal villi; the cysts found in North America, they are be- boo shoots, which are eaten raw or are passed in the feces. Once a cyst is coming more widely known as a result peeled in the mouth.9 The life cycle of ingested, its cytoplasm undergoes a ofthe increasing Asian immigration to F. buskiis similar to that ofF. hepatica. number of changes that result in two North America.'3 * Epidemiology: This organism is trophozoites. The trophozoites can * Diagnosis: Identification of ovoid mainly restricted to the Orient (China, also reproduce by binary fission. This operculated eggs with a terminal spine Taiwan, Vietnam, Thailand, Malaysia, capability results in many organisms from the feces or from duodenal aspi- and India). Dogs, pigs and rabbits are inhabiting the host's gut.'3 rates establishes the diagnosis.'3 common reservoirs.'3 * Pathology and symptoms: The * Treatment:Praziquantel* 25 mg/kg * Pathology and symptoms: These symptoms most commonly associated tid x 1 d for both adults and children is parasites attach to the host's bowel with this parasitic infection are nausea, the recommended treatment.'2 mucosa and feed on the columnar epi- abdominal bloating, cramps, thelial cells, causing ulceration and flatulence, diarrhea, and weight loss. sometimes hemorrhage. Small parasite Malabsorption is also associated with Fasciola hepatica (sheep liver fluke) loads are usually asymptomatic, but as G. lamblia infection,24 as is atrophy of * Disease: Fascioliasis. the extent ofinfection increases, symp- the intestinal villi. Symptoms usually * Mode ofacquisition: Infection oc- toms may include profound abdomi- subside within fourdays to a week after curs through consumption of water- nal pain, profuse, yellow, fatty stools infection, but may persist until the ap- cress or similar vegetation contami- indicative of malabsorption syn- propriate therapy is initiated.24 nated by metacercariae. The metacer- drome, B12 deficiency, and obstruc- * Epidemiology: Giardia lamblia are cariae hatch in the host's small tion ofthe ampula ofVater and the gut distributed world wide, but the disease intestine, releasing larvae which enter lumen. frequently is most common where hygienic prac- the liver and mature to adults which occurs.'6 tices are poor. It is transmitted through feed on hepatocytes, the liver par- * Diagnosis: Examination of the fecally contaminated food and water. enchyma, or the bile duct. Fertilized host's stools for eggs is the only diag- G. lamblia is a particular problem but unembryonated eggs are passed nostic method, but differentiation among homosexual men who fre- through the bile duct into the intestine from F. buski eggs and the eggs ofsome quently indulge in oral-anal contact, and out in the feces. Once in the fresh ofthe Echinostoma group is difficult.'3 nursing-home residents, children at water, they hatch and release mira- * Treatment: Praziquantel*, 25 mg/ day-care centres,8 and persons who cidia, which penetrate the host snail kg tid x 1 d for both adults and children drink water from lakes and streams (members of the Lynnea species), 13 is the treatment of choice. Alter- without taking appropriate precau- where the cercariae evolve before leav- natively, niclosamide* (in the form of tions to decontaminate it. Water ing the snail and encysting on water- tablets which must be chewed thor- sources are frequently contaminated cress. There they become the metacer- oughly) maybe given in a single dose of by beavers and other wild animals caria which are ingested by humans 2 g for adults. A single dose of 1 g is which defecate in them.25 and other mammals, such as sheep. recommended for children weighing * Diagnosis: Identification of the * Pathologyandsymptoms: Infection 11-34 kg and a single dose of 1.5 g for trophozoite or cyst in the patient's may cause fever, malaise, nausea, children weighing more than 34 kg.'2 stool establishes the diagnosis. If

CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 623 clinical intuition suggests G. lamblia tion ofstool samples or scrapings from petent hosts suffer from a cholera-like and stool examination is negative-a the colonic ulcer base for the presence fulminant diarrhea with non-bloody not uncommon occurrence-the En- ofcysts or trophozoites is the primary stools, dehydration, malabsorption, terotest26 may be helpful. If this test, method ofdiagnosis. This is a difficult and weight loss.30,3' In these patients, too, proves negative, but intuition still procedure requiring considerable tech- symptoms may persist for more than suggests G. lamblia, aspirated duo- nical expertise. Charcot-Leyden four months. The immune system denal material may be examined for crystals (which are the products ofde- plays a very important part in control- trophozoites.'3 generated eosinophils) are also often ling this parasitic organism, as evi- * Treatment: The recommended found in the stools ofhosts canrying the denced in the marked difference be- treatment is quinacrine HC1 100 mgtid colonic infection ofE. histolytica.9 Ex- tween the symptoms and their p.c. x 5 d for adults and 2 mg/kg x 5 d traintestinal amebiasis is detected by duration in immunologically compe- for children (to a max. 300 mg/day). serologic techniques such as indirect tent and incompetent hosts. An alternative therapy is metro- hemagglutination, indirect immu- * Diagnosis: Identification of Cryp- nidazole 250 mg tid x 5 days for adults nofluorescence, ELISA, and the comple- tosporidium oocysts in the host's stool and 5 mg/kg tid x 5 d for children.'2 ment fixation test.28 sample establishes diagnosis. To iden- * Treatment: In cases of tify the oocysts is not a simple task, as asymptomatic amebiasis, the treat- they have to be isolated by centrifuga- * Disease: Amebiasis. ment of choice is a 20-day course of tion, then stained and further identi- * Mode ofacquisition: Infection oc- iodoquinol***, 650 mg tid for adults fied microscopically. Although the curs by means of ingestion of fecally and 30-40 mg/kg/day in 3 doses for Cryptosporidium oocysts are larger contaminated material containing the children. For patients with intestinal than yeast cells, they can be easily con- cyst ofE. histolytica. The trophozoites disease or a hepatic abscess, this treat- fused with yeast if the technologist is migrate from the small intestine to the ment should be combined with a 10- not specifically told to look for them. A large intestine, where they encyst and day course of , 750 mg fluorescent antibody test is another undergo nuclear division. Cysts are tid for adults and 35-50 mg/kg/day, available diagnostic tool.29 passed in the host's feces.'3 given in 3 doses for children. Only the * Epidemiology: Cryptosporidium * Pathology and symptoms: Once in drugs ofchoice are mentioned because most often infects vertebrate hosts, in the large intestine, the trophozoites can the list ofalternatives is extensive (con- particular, young or immu- encyst and divide, or they can invade sult Reference 12). nocompromised individuals. Out- the colonic mucosa to produce the clas- Cryptosporidium species breaks have been noted in animal han- sic, flask-shaped, colonic ulcer. Subse- dlers, children attending day care, quently, they may be distributed sys- * Disease: Cryptosporidiosis. travellers in foreign countries, and im- temically. This process results in extra- * Modeofacquisition: Infection is ac- munosuppressed persons or persons intestinal complications. The common quired by consumption offecally con- with AIDS.30'31 complication of acute amebiasis in- taminated material which contains the * Treatment: Broad-spectrum antibi- cludes bloody and mucoid diarrhea oocysts of Cryptosporidium. The otics, antihelminthics, with abdominal pain, cramping, and oocysts arrive in the host's small intes- agents, and coccidiostats have been flatulence. Visual inspection of the tine and release their sporozoites. The tried with little effect. Researchers are colonic mucosa reveals the classic sporozoites locate themselves beneath currently experimenting with spi- flask-shaped lesion. The patient with the intestinal epithelial cells, producing ramycin 1.0 g tid x 21 days. chronic amebiasis may suffer from in- merozoites which can produce either termittent diarrhea and constipation. more merozoites or microgametocysts, Dientamoebafragilis Fulminant attacks ofamebic disentery which, in turn, release microgametes. * Disease: Dientamoebiasis. are more frequently reported in immu- Male and female microgametes fuse, * Mode ofacquisition: Since D. frag- nocompromised patients than in oth- yielding a zygote which develops into ilis lacks a cyst stage, it is believed to be ers. Amebic is the most an oocyst. Most oocysts develop a transmitted inside helminth eggs, in common extraintestinal manifestation thick protective wall which allows for particular those of Enterobius ver- ofamebiasis. Complications ofamebic passage in the feces and survival in the micularis.32 The finding ofD. fragilis- liver abscess include amebic lung ab- environment. Those that do not de- like structures in pinworm eggs sup- scess, pericarditis, empyema, and velop this wall rupture within the intes- ports this belief, since co-infection is amebic . These diseases re- tine, further escalating the intrain- often observed with these two sult from direct extension of the testinal infection.29 organisms. D. fragilis is found in the hepatic disease. Brain abscess is also a * Pathology and symptoms: Al- crypt of the host's large intestine. serious complication.'6 though the is the most fre- Transmission occurs through fecal- * Epidemiology: This parasite is dis- quently involved site ofinfection, any oral contact. tributed world wide but is more com- part ofthe may be * Pathology and symptoms: D. frag- mon in developing countries and in involved. Clinical features are gener- ilis, long believed to be a harmless areas of poor sanitation and crowd- ally either non-existent or consist of a commensal, has been associated with ing.'6 It is more common, too, among slight, crampy, abdominal pain, with abdominal discomfort, flatulence, di- developmentally handicapped persons some bloating and self-limited diar- arrhea and bloody, mucoid, and loose who live in institutions, homosexuals, rhea which lasts one to 10 days (or stools.32 Since it is incapable of tissue and persons with unhygienic longer) in immunologically competent penetration, it may merely act as a con- practices.27 patients and is accompanied by a low- stant irritant, stimulating colonic * Diagnosis: Microscope examina- grade fever. Immunologically incom- motility.

624 CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 * Epidemiology: This parasite is cos- clinical judgement suggests B. coli, ***Iodoquinol is marked in Canada by mopolitan in its distribution, with an stool samples may be cultured on spe- G.D. Searle & Co., Ltd., Oakville, Ont. increased prevalence in children, ho- cial media. mosexuals, and persons living in * Treatment: Treatment may consist Acknowledgements institutions. oftetracycline, 500 mg qid x 10 days for * Diagnosis: Diagnosis is established adults and 10 mg/kg qid x 10 days (to a The authors wish to thank Dr. G.F. by means of microscopic stool exam- max. 2 g/day) for children. Alter- White, Bureau ofHuman Prescription inations for the trophozoite. The natives include iodoquinol, 650 mg tid Drugs, Health Protection Branch, Ot- trophozoite should be stained with x 20 days for adults and 40 mg/kg/day tawa, Ontario, for his advice on cur- iron hematoxylin stain to accentuate in 3 doses x 20 days for children, or rently available drugs in the characteristic features of the para- metronidazole, 750 mg tid x 5 days for Canada. We also appreciate the assist- site. These include a large number of adults and 35-50 mg/kg/day in 3 doses ance of Peter King, Editorial Services, binucleate organisms and nuclei con- x 5 days for children.'2 Dalhousie University, in the prepara- taining four to eight chromatin gran- tion ofthis manuscript. ules centrally located and lacking pe- Isospora belli ripheral chromatin.9 * Disease: Isosporiasis. References * Treatment: A recommended treat- * Mode ofacquisition: This parasitic ment is iodoquinol, 650 mg tid x 20 d 1. Turner JA. Drug therapy of gastroin- infection is acquired by ingestion of testinal parasitic infections. Am J Gastroen- foradults or 40 mg/kg/d in 3 doses x 20 material contaminated with the oocyst. terol 1986; 81:1125-37. d for children. Alternatively, The life cycle ofthe parasite is similar be in the 2. Embil JA, Pereira LH, White FMM, et al. tetracycline may given to that of Cryptosporidium sp., except Prevalence ofAscaris lumbricoides infection amounts of 500 mg qid for 10 d for that I. belli has a sporocyst stage not in a small Nova Scotian community. Am J adults and 10 mg/kg qid x 10 d for seen in Cryptosporidium sp.'3 Trop Med Hyg 1984; 33:595-8. children.12 * Pathology and symptoms: Symp- 3. D'Intino AF, Embil JA. Where are you toms are usually noticeable within one going? Where have you been? Nova Scotia Balantidium coli week of infection. They range from Med Bull 1980; 59:52-6. * Disease: Balantidiasis. minimal gastrointestinal manifesta- 4. Quinn TC, Gender BS, Bartlett JG. New DM . Modeofacquisition: Infection is ac- tions to severe .33 A malab- developments in infectious diarrhea. quired by means of ingestion of con- sorption syndrome may occur, result- 1986; 32:165-244. taminated food orwater containing the ing in fatty stools and weight loss.33 5. Ching HL Fish tapeworm infections (di- * Epidemiology: The distribution of phyllobothriasis) in Canada, particularly B. coli cyst. Trophozoites encyst in the British Columbia. Can Med Assoc J 1984; host's stomach and small intestine but this parasitic infection is cos- 130:1125-7. live in the large intestine. They re- mopolitan, though it occurs more com- monly in children and male homosex- 6. Kwee HG, Sautter RL. Anisakiasis. Am producebybinary fission in the colonic Fam Phys 1987; 36(2):137-40. lumen, encyst, and are shed into the uals than in other individuals. environment via the stool.9 * Diagnosis: Microscopic identifica- 7. Sweeny B, Langlois L, Breton JP, et al. in Outbreak oftrichinosis associated with con- * Pathology and symptoms: Balan- tion ofthe classic oocysts the host's sumption of bear meat, Sherbrooke, Que. tidium coli is the largest protozoan par- stools establishes the diagnosis. If the Can Dis Wkly Rep 1977; 3:81-2. microscopic examination yields nega- asite infecting humans.'3 It can pro- 8. Keystone JS, Krajden S, Warren MR. duce an asymptomatic infection, or it tive results, the Enterotest may be used Person-to-person transmission of Giardia can invade the colonic mucosa, pro- to try to recover I. belli oocysts. lamblia in day-care nurseries. Can MedAs- ducing crater-like ulcers resembling * Treatment: Trimethoprim-sul- soc J 1978; 119:241-2, 247-8. those caused by E. histolytica.'6 famethoxazole, 160 mg TMP, 800 mg 9. Markell EK, Voge M, John DT. Medical Clinical features range from a vague SMX qid x 10days then bid x 3 weeks is parasitology. (6th ed.) Philadelphia: W.B. abdominal discomfort to a fulminant the recommended treatment.'22 Saunders, 1986. diarrhea (in the immune-compro- 10. Blumenthal DS. Intestinal nematodes in mised host).16 Perforation ofthebowel, the United States. N Engl J Med 1977; secondary peritonitis, and subsequent *To obtain either of these agents for 297:1437-9. death have occurred. trematode infections, one must contact 11. White FMM, Pereira LH, EmbilJA, et al. Miles 77 Belfield Scotia. Can J * Epidemiology: B. coli has a cos- Pharmaceuticals, Ascaris lumbricoides in Nova mopolitan distribution, and epidemics Road, Etobicoke, Ont. M9W 1G6. Pub Health 1986; 77:201-4. in (416) 248-0771. Because of different 12. Drugs for parasitic infections. Medical have been reported mental institu- the of 28:9-16. tions and day-care centres, where close distribution rights, supplier Letter 1986; human contact and unhygienic han- praziquantel for other infections is 13. Noble ER, Noble GA. Parasitology: the E.M. Pharmaceuticals Inc., 5 Skyline biology ofanimal parasites. (5th ed.) Phila- dling offecal material have been asso- U.S.A. delphia: Lea & Febiger, 1982. ciated with person-to-person transmis- Drive, Hawthorne, New York, reservoir (914) 592-4660. 14. Simon RD. Pinworm infestation and uri- sion. The pig is the presumed nary tract infection in young girls. Am JDis ofthis infection.9 **This product must be obtained Child 1974; 128:21-2. * Diagnosis: Diagnosis is established through Dr. G.F. White, Bureau of Human Prescription Drugs, Health 15. Evans JAR, Embil JA. Prevalence of by means ofmicroscopic identification Enterobius vermicularis in a population ad- *ofthe characteristic trophozoite or cyst Protection Branch, Tower "B", Place mitted to the Izaak Walton Killam Hospital in the host's stool samples. If micro- Vanier, 355 River Road, Vanier, Ont. for Children, Halifax, Nova Scotia. Nova scopic examination is negative, but K1A 1B8. (613) 993-3660. Scotia MedBull 1975; 54:159-61. CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988 625 Intermediate Prescribing Information Symptoms and Treatment of Overdosage Slow-K® Symptoms: especially where excretory mechan- (slow-release potassium chloride) isms are impaired or if potassium is adminis- 16. WHO Scientific Group on Intestinal Potassium supplement tered too rapidly intravenously, potentially fatal Protozoan and Helminthic Infections. Intes- hyperkalemia can result (See CONTRAIN- tinal protozoan and helminthic infections: Indications DICATIONS and WARNINGS), which is usually report of a WHO Scientific Group. WHO Hypokalemia with metabolic alkalosis, digitalis asymptomatic and may be manifested only Tech Rep Ser 1981; 666. intoxication. Prevention of potassium depletion by an increased serum potassium concentration k when dietary intake is insufficient in patients and characteristic electrocardiographic 17. Ozere RL, van Rooyen CE, Roy DL, et on digitalis and diuretics for the treatment of changes (peaking of T-waves, loss of P-wave, al. Human trichinosis: studies on eleven congestive heart failure, hepatic with depression of S-Tsegment, and prolongation cases affecting two families in Nova Scotia. ascites, selected patients on long-term diuretic of the QT interval). Late manifestations include Can MedAssoc J 1962; 87:1353-62. therapy, hyperaldosteronism states with normal muscle paralysis and cardiovascular collapse renal function, the nephrotic syndrome, certain from cardiac arrest. Discontinue SLOW-K 18. Appleby D, Kapoor W, Karpf M, et al. diarrheal states. immediately. Anisakiasis: nematode infestation produc- Contraindications Treatment: (1) elimination of foods and medica- ing small-bowel obstruction. Arch Surg Renal impairment with oliguria or azotemia, tions containing potassium and potassium- 1982; 117:836. untreated Addison's disease, hyperadrenalism sparing diuretics; (2) IV. administration of 300 associated with adrenogenital syndrome, to 500 ml/hr of 10% dextrose solution contain- 19. Smith JW, Wootten R. Anisakis and extensive tissue breakdown as in severe bums, ing 10-20 units of insulin per 1,000 ml; (3) cor- anisakiasis. Adv Parasitol 1978: 16:93-163. acute dehydration, heat cramps, adynamia rection of acidosis, if present, with intravenous episodica hereditaria, hyperkalemia of any etio- sodium bicarbonate; (4) use of exchange 20. Cline BL Current drug regimens for the logy, certain cardiac patients with esopha- resins, hemodialysis, or peritoneal dialysis; (5) treatment ofintestinal helminth infections. geal compression due to an enlarged leftatrium, calcium gluconate. Med Clin North Am 1982; 66:721-42. dysphagia. In patients stabilized on digitalis, too rapid a Cause for arrest or delay in tablet passage lowering of the serum potassium concentration 21. Fish tapeworm infection-United through the gastrointestinal tract (liquid potas- can produce digitalis toxicity. States. Can Dis Wkly Rep 1976; 2:166-7. sium should be given in such cases). Dosage and Administration Warnings Usual dietary intake of potassium bythe aver- 22. McFadzean AJS, Yeung RTT. Acute In patients with impaired mechanisms for age adult is 40 to 80 mEq per day. Potassium pancreatitis due to Clonorchis sinensis. excreting potassium, eg. chronic renal disease, depletion sufficient to cause hypokalemia Trans R Soc Trop Med Hyg 1966: 60:466- careful monitoring of serum potassium and usually requires the loss of 200 or more mEq of 70. dosage adjustment can prevent hyperkalemia potassium from the total body store. 23. WG. Clinical manifestations of and cardiac arrest. Prevention of hypokalemia: usual dosage 20 Strauss Do not treat hypokalemia with potassium salts mEq daily. clonorchiasis: a controlled study of 105 and a potassium-sparing diuretic concomitant- Treatment of depletion: usual dosage 40-100 cases. Am J Trop MedHyg 1962; 11:625-30. ly, since severe hyperkalemia may result. Use mEq daily. 24. Brasitus TA. Parasites and malabsorp- an alkalinizing potassium salt such as potassium Usual dosage range: 2-6 tablets daily, preferab- Am JMed 67:1058-65. acetate, potassium bicarbonate, orpotassium ly after meals. Do not exceed 12 tablets daily. tion. 1979; citrate in hypokalemia with metabolic acidosis. Dosage Forms 25. Weniger BG, Blaser MJ, Gedrose J, et al. A probable association exists between the SLOW-K: pale-orange, sugar-coated, slow- An outbreak ofwaterborne giardiasis associ- use of coated tablets containing potassium salts, release tablets each containing 600 mg of ated with heavy water runoffdue to warm with or without thiazide diuretics, and the potassium chloride (equivalent to 8 mEq of Am J incidence of serious small bowel ulceration. Such potassium), branded SLOW in black ink weather and volcanic ashfall. Public preparations should be used only when Availability K Health 1983; 73:868-72. adequate dietary supplementation is not practi- Bottles of 100,1,000 and 5,000. 26. Beal CB, Viens P, Grant RGL, et al. A cal, and should be discontinued if abdominal Product monograph available on request. new technique for sampling duodenal con- pain, distention, nausea, vomiting or gastroir.- References: tents: demonstration of upper small-bowel testinal bleeding occurs. SLOW-K is a wax 1. Geigy Scientific Tables Volume #1, 'Units of measurements, body fluids, composition of the body, nutrition' 1981: Page 245. pathogens. Am J Trop Med Hyg 1970; matrix tablet formulated to provide a controlled 2. Stanaszek WF, Romankiewicz JA. Current approaches to 19:349-52. rate of release of potassium chloride and management of potassium deficiency. Drug Intell Clin Pharm thus to minimize the possibility of a high local 19:1985; 176-184. 27. PomerantzBM, MarrJS, GoldmanWD. 3. Kopyt N. et al. Renal retention of potassium in fruit. N.E.J.M. concentration of potassium near the bowel 313 (a): 1985; 582-583. Amebiasis in New York City 1958-1978. wall. While the reported frequencyof small bowel 4. Skoutakis VA. et al. Liquid and solid potassium chloride. Identification ofthe male homosexual high lesions is very much less with wax matrix Bioavailability and safety. Pharmacotherapy 4:1984; 392-397. risk population. Bull NY Acad Med 1980; tablets (less than one per 100,000 patient years) 56:232-44. than with enteric-coated potassium chloride tablets (40-50 per 100,000 patient years), a few 28. Patterson M, Healy GR, Shabot JM. cases associated with wax matrix tablets have Serologic testing for . Gastroen- been reported. terology 1980; 78:136-41. Discontinue immediately and consider the pos- 29. Embil JM, Embil JA. Cryptosporidium sibility of bowel obstruction or perforation if 66:109- severe vomiting, abdominal pain, distention or today. Nova Scotia Med Bull 1987; gastrointestinal bleeding occurs. M~~~~~~~ 11. Precautions SLOW-K® 30. Whiteside ME, BarkinJS, MayRG, et al. The treatment of potassium depletion, particu- Enteric coccidiosis among patients with the lariy in the presence of cardiac disease, renal acquired immunodeficiency syndrome. Am disease or acidosis, requires careful attention to J Trop MedHyg 1984; 33:1065-72. acid-base balance and appropriate monitor- Gives back ing of serum electrolytes, the electrocardiogram 31. Fischer MC, Agger WA. Cryp- and the clinical status of the patient. tosporidiosis. Am Fam Phys 1987; Use with caution in diseases associated with what 36(4):201-4. heart block since increased serum potassium may increase the degree of block 32. YangJ, Scholten TH. Dientamoebafrag- Adverse Reactions diuretics iis:a reviewwith notes on its epidemiology, Small bowel lesions: the incidence is much pathogenicity, mode of transmission, and lower than that reported for enteric-coated po- |diagnosis. Am J Trop MedHyg 1977; 26:16- tassium chloride tablets (See WARNINGS). often 22. Most common: nausea, vomiting, abdominal discomfort, and diarrhea; best avoided by take away. 33. Liebman WM, Thaler MM, DeLorimier increasing fluid intake when possible, taking A, et al. Intractable diarrhea of infancy due the dose with meals or reducing the dose. to intestinal coccidiosis. Gastroenterology Most severe: hyperkalemia (See WARNINGS), 11980; 78:579-84. esophageal and gastrointestinal obstruction, Mississauga, Ontano L5N 2W5 c-s60s2 bleeding or perforation (See WARNINGS). CAN. FAM. PHYSICIAN Vol. 34: MARCH 1988