an ever-increasing knowledge of all aspects of insect-borne diseases has pro- vided the foundations essential to the success of applied control measures. Insects and Seemingly the major limiting factor in the achievement of unprecedented, Helminths constructive victories is the modest eco- nomic burden that would be tempo- Everett E. Wehr, John T. Lucker rarily imposed.

GERARD DIKMANS^ a graduate veter- Many species of the helminths, or inarian from Michigan State College parasitic worms, of livestock and poul- and holder of a master's degree from try can pass through certain of their Minnesota and a doctor's degree from early stages only within the body of an Georgetown University^ has been a insect. These species are transmitted, parasitologist in the Bureau of Animal in the true sense, by insects. Beetle Industry since igsG. For several years mites or grass mites similarly transmit he has been in charge of investigations others. One species is transmitted by of ruminant parasites. a tick as well as by insects. These par- A. O. FOSTER^ a parasitologist in the ticular species of worms are obligatory Bureau of Animal Industry, is in charge parasites of insects, or their allies, just of anthelmiiitic investigations. He was as truly as they are obligatory parasites trained at the Johns Hopkins Uni- of farm animals or birds. For their con- versity School of Hygiene and Public tinued existence and propagation, for Health and served for 5 years on the their survival as species, they depend staff of the Gor gas Memorial Labora- equally upon insect and upon avian or tory of Tropical and Preventive Medi- mammalian hosts. cine in Panama. The life cycle of a helminth of one C. D. STEIN is a veterinarian in the of these species, like the life cycle of all Bureau of Animal Industry. For many other parasitic helminths, is initiated years he has contributed important re- by the eggs or microscopic larvae pro- searches on anthrax, equine infectious duced by the mature female or her- anemia, and other diseases of large maphroditic individual. But depending and small animals. on its specific identity, its eggs or larvae L. T, GiLTNER^ a veterinarian, is are infectious only to an insect or a pathology consultant in the Bureau of mite or perhaps a tick. If ingested by Animal Industry. He was assistant a suitable insect, for example, each ç^gg chief of the pathological division for or larva gives rise to a more advanced many years and has pursued or directed developmental stage of the parasite, investigations on nearly all aspects of which takes up its abode in some part animal diseases. of the insect's body. There, however, the development of the worm stops at a stage far short of reproductive ma- turity. Unless this arrested-develop- mental stage gains access to the body of a suitable vertebrate animal, the life cycle of the parasite cannot be com- pleted. Obviously, therefore, any step that can be taken to destroy infected insects will aid in preventing the in- fection of livestock and poultry with worms that have this type of life cycle. The world-wide extermination of the Camponotus castaneus, a common ant. insect vectors, were this possible, would 169 170 Yearbook of Agriculture 1952 result automatically in the extermina- parasitic worms, the eggs and larvae tion of a goodly proportion of the spe- of some of the heteroxenous worms of cies of worms that now afflict man and farm animals and birds are not infec- his domestic animals and many others tious to them. Other arthropods, snails, that live in wild animals and birds. slugs, earthworms, or other animals Worms that are obliged to undergo serve as intermediate hosts in those development in two or more hosts are instances. called heteroxenous parasites. The Some of the insect vectors of worms hosts in which they can reach repro- that produce eggs, which leave the ductive maturity are called final or definitive host's body in the manner definitive hosts. Hosts in which their described, habitually feed upon the larval stages must develop before the excrement of higher animals. In the parasites can take up life in a final host process they ingest the worm eggs and are called intermediate hosts. thus become infected. Others are not Some instances of the transmission of susceptible as adults to infection or at parasitic worms by insects were dis- least do not become infected. They covered before it was learned that in- habitually deposit their eggs in excre- sects are also vectors of some of the ment or in materials contaminated by most devastating protozoal and infec- it. The larvae that hatch from their tious diseases known to medical and eggs ingest the worm eggs and are sus- veterinary science. Some years before ceptible to infection by them. In other the transmission of malaria or yellow instances the insects involved cannot fever by mosquitoes or of southern be classified as coprophagous—dung cattle fever by ticks was discovered, it eating—nor do they customarily or had been demonstrated that the larvae preferentially breed in manure. But of a nematodc worm^ Wuchereria natural forces continually scatter worm bancrofti, which causes human filiari- eggs into their habitats. They ingest asis, could be sucked up by a feeding quite incidentally the worm eggs that mosquito and would undergo develop- contaminate their normal food supply. mental transformation in its body. Some of the vectors are themselves Very few kinds of parasitic worms ectoparasites of farm animals. They can multiply—that is, reproduce normally feed upon the cellular debris through successive generations—en- or detritus on the skin of their hosts. tirely within the body of the animal in They take in worm eggs when the skin which they mature. The eggs or larvae is contaminated with fecal matter or of nearly all species must leave the crushed parts of worms. host's body to perpetuate the parasite. Some of the heteroxenous worms live The eggs or larvae of worms that in situations, such as the circulatory live in the digestive tract or in an system or subcutaneous tissues, that organ or system (such as the liver or have no connection with the external respiratory system) that communicates body openings of the host. They include wdth the digestive tract or in the uri- several species of viviparous round- nary system ordinarily pass from the worms, or Nematoda, which eject the host with its feces or urine. The pres- larvae they produce into their host's ence of the progeny of the worms in blood, or lymph, or dermal skin layers. those substances, which in natural cir- There the larvae remain, ultimately to cumstances are deposited by livestock perish unless they are ingested by a and poultry on the ground, leads to biting or bloodsucking insect. their ingestion by various kinds of in- Not only do the habits, habitats, vertebrate and vertebrate animals. and structural modifications of the Although the insects and their close various insects and certain of their close relatives are perhaps the most ubiq- relatives lead these arthropods to ingest uitous of the invertebrates and are of the microscopic progeny of parasitic outstanding importance as vectors of worms of many kinds. The insects like- Insects and Helminths 171 wise afford an almost ideal means of ach worms, Ascarops strongylina and transport of the infectious stages of the Physocephalus sexalatus, of swine, and worms back to the definitive hosts, live- the gullet worm, Gongylonema pul- stock or poultry. Many of them form chrum, which occurs in swine, sheep part of the normal diet of birds. In and cattle, utilize such coprophagous grazing, swine, sheep, cattle, and horses beetles as Copris, Aphodius, Passa- cannot avoid taking in beetles, mites^ luriiSj OnthophagiiSj Scarabaeus, Gym- and similar insects along with the herb- nopleuruSi Ataenius, Canthon, Phan- age they consume. A dog or cat suffer- aeuSy and Geotrupes as intermediate ing from infestation by fleas or lice, hosts. The German cockroach also bites and licks at the noxious creatures serves as an intermediate host of the and swallow^s some of them. A female gullet worm. The eggs ingested by the mosquito must have a blood meal be- insects contain well-developed em- fore it can lay fertile eggs and a further bryos at the time of oviposition. On blood meal between every two batches hatching in the insect's gut, the larvae of eggs it lays. If, between meals, in- first enter the abdominal cavity of the fectious worm larvae have developed intermediate host and finally come to in its body, it injects these into the rest in the w^alls of the Malpighian tu- blood of the next animal it bites. bules or musculature, where they be- Many adaptations exist among in- come encysted. Completely formed sects, parasitic worms, and the defin- cysts are usually found free in the ab- itive hosts of the worms. Farmers dominal part of the body cavity. The can take advantage of some of these larvae become infective in the inter- adaptations to protect livestock and mediate host in a month or so. poultry against the inroads of insect- The larvae of the esophageal worm, borne worm infections. Spirocerca lupi, of the dog develop to the infective stage in the beetle, Scara- INSECTS FREQUENT FECAL and re- baeus sacer, and other beetles. The in- lated waste materials because those fective larvae become encysted in these substances are essential for their growth insects, chiefly on the trachéal tubes. and development or because they con- If such beetles are swallowed by an tain something that attracts insects—a unsuitable host, such as a frog, snake, bright or moving object, for example. bird, or a small mammal, the larval Segments of tapeworms, because of worms become encysted again in the their bright color or ability to move, esophagus, mesentery, or other organs readily attract insects and mites and of these animals. This phenomenon is often are eat@n by them. also known to occur in the case of the Insect-borne worms of livestock and swine stomach worm, Physocephalus poultry include representatives of all sexalafus, the larvae of which have four of the major groups of helminths : been found naturally reencysted in the Roundworms (Nematoda), tapeworms wall of the digestive tract of such birds (Cestoda), thorny-headed worms as the loggerhead shrike, screech owl, (Acanthocephala), and flukes (Tre- and red-tailed hawk in southern Geor- matoda). Those that are transmitted gia and northern Florida. Reencyst- by habitual or accidental dung feeders ment of the larvae was found in experi- inhabit the digestive tract of the defin- ments to occur in many different ani- itive host or organs that communicate mals, including birds, mammals, and with this tract; as has been noted, reptiles, to which beetles containing in- the eggs or larvae of worms living in fective larvae were fed. these situations occur in the host's feces. One of the commonest species of Various species of tumble bugs and tapeworms, Hymenolepis carioca, dung beetles are intermediate hosts for found in the domestic fowl, is trans- worms occurring in swine, sheep, cat- mitted by beetles {Aphodius, Choerid- tle, poultry, cats, and dogs. Two stom- ium, Hister, and maybe Anisotarsus). 172 Yearbook of Agriculture 1952 Another species of tapeworm, Hy- have been reported as being infected menolepis cantaniana, found in chick- with the third-stage larvae of Subu- enSj turkeys, and quail of the Eastern lura bnunpti, the cecal worm of poul- States, develops in the beetles Ataenius try. The final host becomes infected and Choeridium. Its development in through the ingestion of the infected its intermediate host is unusual. The intermediate host and the larvae pass larva elongates to form a somewhat to the cecum, the blind gut. Many branched myceliumlike structure ; buds species of darkling beetles and ground along the branches develop into the beetles have been incriminated as in- cysticcrcoids, or small larval forms, termediate hosts of Raillietin-a cesti- which contain the tapeworm heads. cilluSy the broad-headed tapeworm of Tapeworms belonging to the genera poultry and of another poultry tape- Joyeuxiella and Diplopylidium, which worm, Choanotaenia infundibulum. are closely related to Dlpylidium^ occur The latter also develops in the red- in cats and apparently develop in dung legged grasshopper and in the house beetles and related insects. It takes fly. The chief effect of this tapeworm, about 3 weeks to 2 months, depending even in heavy infestations, is to retard on temperature, for the cysticcrcoids to the growth rate of its host. develop within the insect host. Com- The Surinam roach, and possibly pletely developed cysts are found in its other species of cockroaches, is an in- body cavity. The tapeworm Metrolias- termediate host for three nematodes of thes lucida^ commonly found in the poultry, namely, the eyeworms, Oxy- small intestine of the domestic and wild spirura mansoni and O. parvovum, and turkey, is reported to have the grass- the proventricular worm, Seurocyrnea hoppers Melanoplus sp., Chorthippus colini, of the turkey and bob white longicornisy and Paroxya clavuliger as quail. Infections with the eyeworms intermediate hosts. Guinea fowls are result in a marked irritation, which also susceptible to infection with this interferes seriously with vision. It often tapeworm. is accompanied by continual winking Dermestid beetles, darkling beetles, as if to dislodge a foreign body. The fungus beetles, and other groups of nictitating membrane of the eye be- beetles and several species of grass- comes inflamed and appears as a hoppers have been infected experi- puffy elevation. Heavy infestations may mentally, or found to be infected nat- cause blindness. The German cock- urally with the larvae of the gizzard roach has been s-hown in experiments worm of poultry, Cheilospirura hamu- to serve as an intermediate host for losa. Seurocyrnea colini. This cockroach, the Small numbers of these worms in the red-legged grasshopper, and the dif- gizzard do not produce any serious re- ferential grasshopper have been re- sults. In heavy infections, the lining ported to be suitable intermediate hosts of the gizzard may show ulcérations, for the globular stomach worm, Tet- which may also involve the muscula- rameres americana, of chickens, bob- ture. Soft nodules enclosing the para- white quail, and turkeys. After the eggs sites are often found in the muscular are ingested by the intermediate hosts, portions, especially in the thinner parts the larvae of this stomach worm pass of the gizzard. In the intermediate host, into the body cavity and become quite the infective larva of the gizzard worm active for the first 10 days after in- is found encysted in the musculature fection. They then penetrate the mus- of the body wall, where it is found to cles and become loosely encysted. In be tightly coiled. The infective stage about 42 days, or possibly sooner, the is reached in about 19 days. infective larvae have completed their Darkling beetles [Alphitohius, Gon- development. The vitality of grass- ocephalurriy and Ammophorus), the hoppers is greatly reduced by infections ring-legged earwig, and the hide beetle with this parasite. Some die and some Insects and Helminths m become inactive and an easy prey to After being expelled with the host's birds. The infection is transmitted to feces, the tapeworm eggs must become the bird through the ingestion of the fairly dry and well anchored befortî infected intermediate host. Serious in- the mites can ingest them. The mites fections with these species of stomach usually do not eat the entire egg. They worms have not been noted in do- make a hole in its shell and ingest its mestic birds in the United States. contents. This tapeworm adversely Several species of ants, of the genera affects the growth of infected lambs. Tetramonum and Pheidole, are natu- Several investigators have reported rally infected with cysticercoids of two that M. expansa produced scouring in closely related poultry tapeworms, range lambs. In experiments, how- Raillictina tetra^onn and R. echino- ever, infected lambs have not shown hothrida. Experimental attempts to in- scouring. fect ants of these and other genera by The life history of M. expansa, feeding to them eggs of these tape- which had defied investigators for worms resulted in failure, but naturally many years, was solved in 1937. Since infected ants were fed to chickens and then it has been shown that oribatid infections resulted. mites also are the vectors of several Quail are said to be seriously parasit- other anoplocephalid tapeworms of ized by R. tetragona and death losses domestic animals. They transmit Cit- have been attributed to this tapeworm, totaenia ctenoides and C. denticulata but its pathogenicity has not been ex- of rabbits; Anoplocephala perfoliata, perimentally verified. A. magna, and Par anoplocephala However, R, echinobothrida is defi- mamillana of horses; and Moniezia nitely known to be one of the most in- henedini and Thysaniezia giardi of jurious tapeworm parasites of poultry. ruminants. It causes the formation of tuberclelike Beetle mites are most apt to be nodules on the intestinal wall, which abundant in moist, shady places. They closely resemble the nodules of tuber- are found in pastures both winter and culosis. The absence of the nodules in summer, but they increase markedly the liver, spleen, and other internal in numbers with the new growth in organs and the presence of tapeworms spring. The mites are generally dis- in the small intestine warrant the diag- tributed throughout the world. nosis of this infection and exclude tuberculosis. THE NUMBER of groups of insects in Biting lice are minor vectors of worm which infection takes place in the lar- parasites. The only known instance in- val or immature stage is small, com- volves the dog biting louse, which is pared to those that acquire the infec- reported to be an intermediate host tion in the adult stage. In some of the double-pored tapeworm, Dipy- instances the mouth parts of the adult lidium caninum, of the dog and cat. insect are of the sucking type so that Because this louse normally feeds on solid materials cannot be ingested, or particles of dried skin of its host, it can its feeding habits are such that it does hardly be classified as a coprophagous not come in contact with materials insect. It is presumed that the skin of containing the worm eggs and larvae. the dog and cat, especially in the peri- The larval insects, however, hatch out anal region, becomes contaminated in such material, and their mouth parts Vvith eggs of the tapeworm, which are are adapted for its ingestion. more or less incidentally eaten by the The house fly and the stable fly breed louse. abundantly in horse manure. Their Beetle mites, also known as oriba- maggots migrate extensively through- tid or galumnid mites, serve as vectors out manure piles and feed promiscu- of the broad tapeworm, Moniezia ex- ously on the materials found therein. pansa, of cattle, sheep, and goats. The maggots of the house fly are the 0701.:M°—52 VA 174 Yearbook of Agriculture 1952 intermediate hosts for two nematodcs the adult flea has sucking mouth parts, ( roundworms ) commonly found in the infection in this stage is impossible. stomachs of horses—Habroiiema inus- Flea larvae ingest the eggs of the tape- cae and Drashia megastoma. Those of worm. In the larva, tïfie tapeworm the stable fly are suitable hosts for the grows but slightly. It grows more in development of a third horse-stomach the pupal stage and transforms into the worm, Habroiiema ma jus. infective stage in the adult flea. The The nematode larvae undergo sev- eral molts within the body of the fíy maggot and reach the infective stage about the time the fly hatches. The adult fly harbors the infective larvae free in the body cavity, but some of the larvae may migrate into the mouth parts of the fly. The horse presumably becomes infected when the flies in White grub. feeding deposit worm larvae on its lips or by ingesting flies which get into its cysticercoid lies free in the body cavity food or water. of the flea. The cat or dog becomes The thorny-headed worm is a rather infected by ingesting fleas or lice. common parasite of swine, particularly in the South. Characteristic nodules MORE THAN one kind of intermedi- form at the sites of attachment of the ate host is required in the development worms to the wall of the small intes- of some of the heteroxenous worms. tine. Sometimes they change their One of them may be an insect—as in places of attachment, thus leaving the the case of the oviduct fluke of poultry, previous sites of attachment to become Prosthogonimus macrorchis, which uti- ulcerative. Perforation of the intestinal lizes a snail. Amnícola limosa parata, vv^all occasionally may occur. The para- as its flrst intermediate host and drag- site makes the intestines worthless for onflies as its second intermediate hosts. sausage casings. White grubs, the lar- Species of several genera of dragonflics, vae of May and June beetles, serve as Leucorrhiniaj Tetragoneuria, Epicor- its intermediate hosts. White grubs arc dulia, and Mesothemisj may serve in found abundantly just below the sur- the capacity of secondary intermediate face of the soil, particularly in grass- hosts for this trematode. lands, and are relished by hogs, which In the United States, the oviduct uncover them as they root up the fluke is found naturally in ducks, Can- ground. ada geese, and chickens, chiefly in the The eggs of the thorny-headed Great Lakes region. Here the snail that worm, which are expelled in the feces is the intermediate host is found in of the swine, hatch when they are in- abundance on the under sides of boards gested by the white grubs. In the grubs, and sticks and may be found traveling the larvae hatching from the eggs arc along the lake bottom in water i to 2 released in the midgut; then they mi- feet deep. grate to the body cavity and there The snail becomes infected by ingest- develop into the infective stage within ing the eggs of the fluke. After going 2 to 3 months in summer. Since the through several stages of development infective larvae persist when the pupal in the snail, the young flukes (cer- and beetle stages of the insect develop, cariae) escape from its body and swim pigs become infected by ingesting in- freely about in the water. The free- fected grubs, pupae, or adults. swimming organisms are draw^n into The larvae of the dog and cat fleas the anal oj^enings of aquatic naiads, are vectors of the double-pored tape- or immature dragonflics, with the worm, Dipylidium caninum. Because water that is alternately taken in and Insects and Helminths forced out by the organs of respiration curs mainly in the right ventricle of located at the posterior end of the ali- the heart and the pulmonary artery of mentary canal. After entrance into the the dog, cat, fox, and wolf. Many body of the naiad, the young flukes studies indicate that it occurs princi- encyst in the muscles and in most in- pally in the Southern States. It may stances are found in the ventral por- occur throughout most of the United tions of the posterior part of the body. States, although not endemically. Infection of the secondary intermedi- Hunting dogs are more seriously af- ate host usually takes place during the fected than other breeds. The infected late spring and early summer, so that animal tires easily, gasps for breath, the young flukes sometimes remain in and may collapse. Severe complica- the insect host for i or 2 years before tions, such as inflammation of the kid- they are ingested by the definitive host. ney and urinary bladder, may arise. Infection of the bird host occurs In severe cases, the animal becomes usually at the end of May or beginning poor, and the hair and skin are dry. of June, when the dragonfly naiads are Abnormal heart sounds are infre- transforming into adults. Infection quently noted, but moist rales are oc- may also occur by the ingestion of in- casionally present. fected mature dragonflies, which can About 24 to 36 hours after the mos- be easily captured by birds in the early quito or flea has sucked blood of an morning. The immature w^orms pass infected animal, the larvae or micro- posteriorly to the diverticulum of the filariae may be found within the tissue cloaca or to the cloaca itself, where cells of the Malpighian tubules. There they develop to maturity. Some of the they develop to the infective stage worms develop to maturity in the ovi- within 5 to 10 days, when they migrate duct and have been found in eggs laid to the mouth parts of the intermediate by infected hens. The presence of this hosts and are ready to be transferred to fluke in laying hens may result in a a final host during the act of biting. sharp drop in ^gg production, the lay- Mosquitoes of the genera Aedes and ing of soft-shelled eggs, and, in ad- Anopheles are vectors for Diroßlaria vanced cases, peritonitis. repenSj a rather small worm occurring Prosthogonimus macrorchis is prob- in the subcutaneous tissue of dogs in ably the most important fluke parasite southern Europe, Asia, and South of poultry in the United States. How- America. The worms may cause pru- ever, it is localized around certain sec- ritis without skin lesions. tions of the Great Lakes region. That The dog sucking louse, the dog flea, is cause for not too great alarm, be- and the brown dog tick have been re- cause the sections arc not important ported as vectors of Dipetalonema re- poultry centers. conditum, originally reported from the perirenal tissue of the dog in Europe. MANY ADULT INSECTS depend on The worm also occurs in other organs blood for food. Among those that have and tissues, including the vascular sys- been reported to be vectors for worms tem, lungs, and liver. The brown dog of livestock are m.osquitoes, midges, tick also transmits D. grassi, which fleas, sucking lice, and ticks. They in- occurs in the subcutaneous tissue and gest worm larvae as they feed on the body cavity of the dog in Italy. blood or lymph of infested animals. All Twelve days after microfilariae of the worms they transmit are round- Dirofilaría scapiceps, which lives under worms of the group Filarioidea. the skin in the loins and in the sub- Mosquitoes of the genera Anopheles, cutaneous tissues of the fore and hind Aedes, and Culex, the dog flea, and the legs of wild rabbits in the United cat flea are suitable intermediate hosts States, had been ingested by Aedes of the dog and cat heartworm. This mosquitoes, infective larvae were seen large worm, 5 to 12 inches long, oc- actively moving in the proboscis of the 176 Yearbook of Agriculture 1952 insects. Microfilariae also were ob- the lesions of both adults and micro- served in the gut contents of an uniden- filariae of Stephanafilaria stilesi, S. de- tified engorged tick. Attempts to infect doesij S. kaeliy and S, assamensis have rabbits experimentally with this round- been reported from the abdomen and worm by allowing infected mosquitoes legs of cattle in North America, Java, to feed on them have failed. The rabbit Malay Peninsula, and India, respec- tick may also be a suitable intermediate tively. Presumably insects transmit host of this worm, although it has not them. been incriminated. The invasion of the skin of sheep by Species of biting midges, or sand the microfilariae of Elaeophora schnei- flies, and black flies have been incrimi- deri, which lives in its host's carotid nated as intermediate hosts of species and iliac arteries, produces a derma- of the genus Onchocerca. O. reticulata titis primarily in the back part of the occurs in various countries in the large head but tending to spread over the tendon supporting the neck of the face to the nostrils. Similar lesions are horse and mule and has been reported sometimes noted on the hind foot used as a possible causative agent of poll evil to scratch the head. The presence oí and fistulous withers. This worm sup- the larvae in the tissues results in in- posedly is transmitted by Culicoides tense itching, which causes the animal nuheculosus. Simulium ornatum is the to scratch itself. The scratching causes vector of Onchocerca gutterosa^ which destruction of tissue. The condition has occurs in the neck tendon and other been confined to summer mountain parts of the body of cattle. Onchocerca ranges in New Mexico, Arizona, Colo- gihsoni, which lives in the subcutane- rado, and possibly Utah. The life his- ous connective tissue of cattle, often tory is unknown, but it is suspected giving rise on the brisket and the ex- that bloodsucking insects serve as in- ternal surfaces of the hind limbs to termediate hosts of the parasite. nodules, in which the worms lie coiled up, is reported to develop in Culicoides IN TI-IK SOLUTION of the problem of pungens and also in black flies. The the control of insect-borne worm infec- microfilariae, infrequently found in the tions of livestock and poultry, six gen- nodules or worm nests, are more often eral avenues of approach are available : found in the walls of the blood vessels The use of drugs thcrapcutically: the and along the lymph spaces. Infected use of drugs prophylactically; physical animals show no symptoms except the and chemical sterilization of stable and nodular swellings under the skin, but poultry manure and sanitary disposal their carcasses are condemned as un- of excrements; elimination of the suitable for sale on most markets. breeding places of insects; destruction The stable fly is a reported vector of insects and their larvae chemically for Setaria cervi, which occurs free in and mechanically; and mechanical the body cavity of cattle and various prevention of the access of insects to species of antelope and deer. This farm animals. worm has been found in the eyes of Although the primary purpose of horses and the udder of a cow. therapeutic treatments directed against Other reports indicate that in Asia the worm infections is to improve the this parasite is transmitted by three health and efficiency of the sick animal, species of mosquitoes {Anopheles hyr- they have some value in control. After cans sinensis. Armigeres ohturhans, treatment, which eliminates worms and Aedes togoi). The last is also a from the animal's body or kills them vector for S, equina of horses. Larvae in the body, there is, until reinfection of both species are said to invade the occurs, a reduction in the number of central nervous system of horses, caus- eggs or larvae voided by the animal ing lumbar paralysis. or the number of larvae entering its Skin lesions due to the presence in tissues. Drugs may be used prophy- Insects and Helminths 177 lactically to combat certain of the in- their larvae are w^eapons that can be sect-borne worm infections. He trazan applied generally to control these vec- administered orally to persons having tors. Usually both lines of attack should filariasis causes a rapid and marked re- be employed, but the habits and life duction in the number of microfilariac histories of insects are so diverse that in the blood even though the adult the weapon of choice—habitat de- worms are not killed. Fouadin, one of struction or larvicide or destruction of the standard drugs in the treatment of the adult—may differ with the insect heartworm infections in dogs^ has a to be fought. similar effect when injected into these Attacks against the house fly can be animals. It also inhibits the reproduc- directed most feasibly and easily tive capacity of the adult female against the larvae. DDT has been re- worms. It is likely that other drugs ported to be effective against the mag- may be found to operate similarly gots of this fly when used in a water against the microfilariac of other emulsion. Such an emulsion w^as found worms of domesticated animals. to be effective also against certain When the economic value of the ani- other species of flies breeding in poul- mal to be protected warrants, stable try manure. DDT, methoxychlor, manure or poultry manure may be chlordane, lindane, and other insecti- promptly collected and stored so as to cides are recommended as residual exclude flics and perhaps other insects sprays directed toward the control of from it. Horse manure may be stored the adults. Important supplemental in piles so that some of the worm eggs measures include disposal of manure, and larvae in it will be destroyed by chemical treatment of manure, the use the heat of its decomposition. This of properly baited fly traps, and the use effect may be heightened by storing it of pyre thrum fly sprays. and cow manure in covered insulated The stable fly likewise is most vul- wooden manure boxes. Evidently it nerable to attack in its larval stage. A has not been determined specifically principal measure for its control— that the eggs and larvae of heteroxc- applicable also in the case of the house nous w^orms are killed by these proce- fly—is the destruction of its breeding dures; however, in all cases investigated places. When it is impossible to locate it has been found that the eggs and and eliminate all of these, insecticides larvae of worm parasites generally are as recommended for controlling the killed by approximately the same de- housefly are distinctly useful against gree of heat (about 140° F.). the adult stable flies. Several chemical agents will kill the Mosquitoes, biting midges, and black eggs and larvae of monoxenous worm flics breed in water, and the elimina- parasites in stable manure. None, to tion of their breeding places is not our knowledge, has been specifically always feasible or desirable. Ponds, demonstrated to be effective against small pools, and useless swampy areas the eggs and larvae of the heteroxenous may often be filled in or drained. worms. Some of the agents do kill as- Since the maintenance of large ponds carid eggs, which are thick-shelled, and and streams is desirable, treating the the means for killing chemically all water with oils to kill the larvae me- types of worm eggs and larvae in ma- chanically and with such larvicides as nure probably are at hand. Investiga- paris green long has been one of the tion to prove this is needed, however. approaches to the problem of mosquito Stable or poultry manure which has control. DDT when incorporated into not been processed in some manner an oily vehicle for application to the ought not be used on the farm for water surface is effective for the fertilizer. destruction of the mosquito larvae. The destruction of breeding places This insecticide also is of value in kill- and direct attacks against insects and ing the adults of mosquitoes, biting 178 Yearbook of Agriculture 1952 midges, and black flies. Tests have in- sible, its practicability seems doubtful dicated that the larvae of black flies It seems probable that other means are susceptible to DDT, TDE, and will have to be sought for the pre- other new chlorinated insecticides. vention of tapeworm infections trans- Cat and dog fleas in and around mitted by these mites. buildings may be controlled eff'ectively EVERETT E. WEIIR is a parasitologist by the use of DDT sprays or dusts. doing research in parasitology in the One to two gallons of 5 percent DDT zoological division y Bureau of Animal in oil sprayed lightly over areas of Industry¡ at Beltsville, Md. He has been 1,000 to 2,000 square feet has been associated with the division since ig28 found effective in the complete eradi- and has been in charge of its investi- cation of adult fleas. Five percent DDT gâtions on the parasitic diseases of powder, applied with a dust can, is poultry since 1936. He is the author of recommended for the destruction of numerous papers on the worms and fleas on dogs. The application of the other parasites of livestock and poultry. dust to the building will destroy the He has particularly investigated the larvae and adults as they emerge. nematodes of birds. Dr. Wehr is a grad- Methods are available for the con- uate of the University of Idaho, trol of grasshoppers, earwigs, and cock- University of California, and George roaches. Beetles frequenting poultry^ Washington University. manure likewise may be controlled JOHN T. LUCKER is a parasitologist chemically. The use of insecticides and has been associated with the zoo- against these beetles probably would logical division since ig^o. He also is not be practical in seeking to control stationed at Beltsville. The identifica- worms in poultry flocks having access tion of nematodes has been one of his to large areas, but the confinement of chief assignments since ig40. He is a birds, as presently widely practiced, graduate of the University of Wash- favors the feasibility of measures for ington and George Washington Uni- beetle destruction in accumulated versity. manure. In theory, beetles frequenting ma- For further reference: Joseph E. Alicata: Early Developmental nure on pastures no doubt also may be Stages of Nematodes Occurring in Swine, dealt with by means of insecticidal U. S. D. A. Technical Bulletin 489^ 1935; dusts or sprays, but we know^ of no The Life History of the Gizzard Worm work demonstrating that this is prac- (Gheilospirura hamulosa) and Its Mode of Transmission to Chickens With Special Ref- tical. Since it has been demonstrated erence to Hawaiian Conditions, in Livro that the feeding of small amounts of Jubilar do Professor Lauro Travassos, 1938, drugs, such as phenothiazine, to cattle Eloise B. Cram: Developmental Stages of prevents the development of horn flies Some Nematodes of the Spiruroidca Parasi- tic in Poultry and Game Birds, U. S. D. A. in their dung, it would seem advisable Technical Bulletin 22/. 1931. to investigate the possibility that beetles Ashton C. Cuckler and Joseph E. Alicata: might be controlled as worm vectors The Life History of Subulura brumpti, a by the routine incorporation of suitable Cecal Nematode of Poultry in Hawaii, insecticidal materials into the diet of Transactions of the American Microscopical Society, volume 63, pages 345-357. 1944- ^ farm animals and birds. Manure de- G. Dikmans: Skin Lesions of Domestic posits on pastures may be broken up Animals in the United States Due to Nema- and spread to reduce the attractiveness tode Infestation, The Cornell Veterinarian, volume 38, pages 3-23. 1948. of the manure to insects. The maxi- R. I. Hewitt, E. White, D. B. Hewitt, S. mum adverse efíccts of dryness and M. Hardy, W. S. Wallace, and R. Anduze: sunlight on w^orm eggs and larvae may The First Year's Results of a Mass Treat- also be had by this step. The chemical ment Program With Hetrazan for the Con- destruction of beetle mites on pastures trol of Bancroftian Filariasis on St. Croix, American Virgin Islands, American Journal and grazing land apparently has not of Tropical Medicine, volume 30, pages been investigated, but even were it pos- 443-452. 1950. Paul R. Highby: Development of the Mi- crofilaria of Dirofilaria scapiceps (Leidy, 1886) in Mosquitoes of Minnesota, Journal of Parasitology (Supplement), volume 24, Insects and the page 36. 1938. Myrna F. Jones: Life History of Metro- liasthes lucida, a Tapeworm of the Turkey, Plant Viruses Journal of Parasitology^ volume ly, page 53> ^930 [part of Proceedings of the Hel- minthological Society of Washington) ; L. D. Christensony Floyd F. Smith Metroliasthcs lucida, a Gestode of Galliform Birds, in Arthropod and Avian Hosts, Pro- ceedings of the Helminthological Society of The Russian scientist D. Iwanowski Washington, volume 3, pages 26-30, 1936; Development and Morphology of-the Ges- demonstrated in 1892 that sap from tode Hymenolepis cantaniana, in Coleop- tobacco plants with a mosaic disease teran and Avian Hosts, with J. E. Alicata, is infectious after passing through a Journal of the Washington Academy of bacteria-proof filter. It was the first dis- Sciences, volume 25, pages 237-247, 1935. Kenneth C. Kates: Development of the covery of an amazing group of agents Swine Thorn-Headed Worm, Macracan- that cannot be seen with ordinary thorhynchus hirundinaceus, in its Interme- microscopes and that now are called diate Host, American Journal of Veterinary viruses. Many of our most serious and Research, volume 4, pages 173-181, 1943; Observations on Oribatid Mite Vectors of difficult plant-disease problems have Moniezia expansa on Pastures, with a Re- been shown to be the results of infec- port of Several New Vectors from the tions of plants by these minute entities, United States, with C. E. Runkel, Proceed- which are smaller than bacteria. A few ings of the Helminthological Society of Washington, vol. 15, pp. 10, 19-33, ^94^- of the many different kinds of viruses H. E. Kemper: Filarial Dermatosis of are even smaller than the largest mole- Sheep, North American Veterinarian, vol- cules known to chemists. ume 19, No. 9, pages 36-41. 1938. Tulip mosaic, peach yellows, aster Wendell PI. Krull: Observations on the Distribution and Ecology of the Oribatid yellows, sugar-beet curly top, phloem Mites, Journal of the Washington Academy necrosis of elm, tobacco mosaic, rasp- of Science, volume 29, pages 519-528. 1939. berry mosaic, blueberry stunt disease, George W. Luttermoser: Meal Beetle potato leaf roll, pea mosaic, tomato Larvae as Intermediate Hosts of the Poultry Tapeworm Raillietina ccsticillus, Poultry spotted wilt, and sugarcane mosaic are Science, volume 19, pages 177-179. 1940. examples of plant diseases caused by Ralph W. Macy: Studies on the Taxon- viruses. Virus agents also cause serious omy, Morphology, and Biology of Prostho- diseases of man and animals—small- gonimus macrorchis Macy, A Common Ovi- pox, measles, mumps, the common duct Fluke of Domestic Fowls in North America, Minnesota Agricultural Experi- cold, rabies, distemper, and foot-and- ment Station Technical Bulletin 98. 1934. mouth disease. Others, like the sac- Horace W. Stunkard: The Life Gycle of brood virus of honey bees, infect in- Anoplocephaline Gcstodcs, Journal of Para- vertebrate animals. sitology, volume 23, page 569, 1937; The Development of Moniezia expansa in the For a long time we knew little about Intermediate Host, Parasitology, volume 30, the nature of viruses. Now, as a result pages 491-501, 1939. of the studies of W. M. Stanley, F. C. William A. Summers: Fleas as Accept- Bawden, N. W. Pirie, and others, they able Intermediate Hosts of the Dog Heart- worm, Dirofilaria immitis, Proceedings of are believed to consist of complex the Society of Experimental Biology and nucleoproteins that have some of the Medicine, volume 43, pages 448-450. 1940. attributes of living organisms. Like liv- Y. Tañada, F. G. Holdaway, and J. H. ing organisms, the individual virus Quisenberry: DDT to Control Flies Breed- ing in Poultry Manure, Journal of Economic particles can reproduce or multiply. Entomology, volume 43, pages 30-36. 1950. They also can change or mutate dur- Willard H. Wright and Paul C. Under- ing the multiplication process. They wood: Fouadin in the Treatment of Infes- do not seem able to grow or multiply, tations With the Dog Heartworm, Dirofi- laria immitis, Veterinary Medicine^ volume however, except within the living cells 29, pages 234-246. 1934. of their hosts, and, unhke living or- 179