Giardiasis: Clinical and Therapeutic Aspects

Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from Gut, 1977, 18, 343-350

Giardiasis: clinical and therapeutic aspects

S. G. WRIGHT, A. M. TOMKINS, AND D. S. RIDLEY From the Hospital for Tropical Diseases, London, and Clinical Nutrition and Metabolism Unit, Department ofHuman Nutrition, London School of Hygiene and Tropical Medicine, London

SUMMARY Malabsorption was present in 29 of 40 symptomatic patients with giardiasis. Twenty- three had impaired D-xylose absorption; in 20 vitamin B12 absorption was low, and 15 patients had steatorrhoea. More severe malabsorption was associated with more marked histological abnormalities. Metronidazole, 2-0 g as a single daily dose on three successive days, produced a parasitological cure rate of 91%. In contrast, the standard course of mepacrine, 100 mg thrice daily for 10 days, eradicated the parasite in only 63% of patients. Improvements in absorption and jejunal morphology followed anti-giardial treatment. Tetracycline in eight patients failed to eradicate the parasite, intestinal absorption was unaltered, and histological appearances of the jejunal mucosa often deteriorated.

Giardia lamblia, a flagellate protozoan parasite of Methods the human upper small bowel, is commonly associated with diarrhoea in the tropics (Antia et al., PATIENTS 1966; Ingram et al., 1966; Kapoor and Mody, Forty adult Caucasians with giardiasis, 26 males and 1968), though symptomatic giardiasis is reported 14 females, were studied. Half were young adults http://gut.bmj.com/ from temperate areas (Moore et al., 1969; Brodsky who had acquired the infection during overland et al., 1974; Brady and Wolfe, 1974). The most travels in Africa, India, or other parts of Asia. This common symptoms reported are abdominal dis- group usually took locally available food and water. comfort, abdominal distension, diarrhoea with Three subjects were infected on brief trips to Lenin- soft, offensive, yellow stools, and lassitude. grad, USSR. The remainder were businessmen, In experimental infections of prison volunteers, academics, or technical assistance personnel who had Rendtorff (1954) found that spontaneous eradication worked in Africa or Asia (Fig. 1). They usually on September 25, 2021 by guest. Protected copyright. of the parasite was the rule but clinical experience adhered to a more Western diet and life-style when indicates that patients may be infected and sympto- abroad. These 40 subjects represent a consecutive matic for several years (Alp and Hislop, 1969). It is series of patients with giardiasis initially investi- likely that immunological mechanisms may be gated because they had profuse diarrhoea of un- involved in the process of eradication (Hermans determined cause or severe diarrhoea and giardiasis et al., 1966; Ament and Rubin, 1972). or symptoms suggestive ofmalabsorption. They were Malabsorption of D-xylose and fat is well docu- investigated at varying intervals after their arrival in mented in giardiasis (Amini 1963; Yardley et al., Great Britain. 1964; Alp and Hislop, 1969; Ament and Rubin, In eliciting histories particular attention was paid 1972; Tewari and Tandon, 1974). Vitamin B12 to symptoms referable to the gastrointestinal tract. malabsorption has been uncommon in previous Clinical evidence of vitamin deficiency and mal- reports (Antia et al., 1966; Ament and Rubin, 1972; nutrition was noted from the history and physical Ament, 1972; Notis, 1972;Tewari and Tandon, 1974). examination. Evidence of recurrent infections or We report here the findings in a consecutive series gastrointestinal symptoms in the past was sought. of patients with giardiasis in whom malabsorption Sigmoidoscopic examinations were performed in all was common and vitamin B12 malabsorption was cases. particularly frequent. Routine haematological and biochemical investigations, including serum protein levels, plasma transaminase and bilirubin levels were performed in Received for publication 15 December 1976 all patients. Serum immunoglobulin levels were 343 Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from 344 S. G. Wright, A. M. Tomkins, and D. S. Ridley

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Fig. 1 The distribution ofgeographical regions in which patients were infected. One patient was infected in the Caribbean. M-0 = 0; M-1 = 0; M-2 = X. on September 25, 2021 by guest. Protected copyright. a 6' measured by radial immunodiffusion. Serum B12 absorption was assessed by urinary D-xylose and folate levels were estimated. excretion after a 25 g oral load, by Schilling tests Stool samples were examined microscopically using 58Co-labelled vitamin B12 with hog intrinsic after formol-ether concentration (Allen and Ridley, factor and by faecal fat excretion over a 72 hour 1970) for cysts, ova, and larvae of parasites. Stools period during which patients consumed a diet were cultured for bacterial pathogens. Barium follow- containing 100 g of fat per day. Stool weights were through examinations were used to demonstrate recorded during this time. anatomical or inflammatory small bowel lesions. Using a Quinton biopsy instrument or a Watson 14C glycocholate breath tests were done as an in biopsy capsule, modified by the addition of an vivo test for bile salt deconjugation (Fromm and aspirating tube, jejunal fluid and jejunal biopsies Hofman, 1971). were obtained under fluoroscopic control from the Patients were investigated in a metabolic ward so first loop of the jejunum. Direct microscopy of that particular attention was paid to obtaining uncentrifuged, freshly obtained specimens of jejunal complete collections for absorption tests. Intestinal aspirate was performed looking for trophozoites or Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from

Giardiasis: clinical and therapeutic aspects 345 pre-cysts of Giardia lamblia. When the biopsy tropical sprue (TS). These groups have been des- capsule was retrieved, any flecks of mucus adhering cribed in detail elsewhere (Tomkins et al., 1974; to the capsule or biopsy were mounted in saline Tomkins et al., 1975). Student's t test was used for under a cover slip for direct microscopy as above statistical comparison of results. (Brady and Wolfe, 1974). The mucosal surface of a portion of the biopsy was smeared on a slide, then Results covered with saline and a cover slip for examination by direct microscopy (Kamath and Murugasu, 1972). G. lamblia was the only parasitic pathogen found A piece of the biopsy was homogenised in glycerol in these patients and no bacterial pathogens were transport medium and stored at - 20°C after rapid isolated by stool culture. The parasitological freezing for bacteriological studies (Drasar et al., diagnosis was made on stool examination in 34 1969). The remainder of the biopsy was orientated patients (85% of the whole group). Cysts were not mucosal side uppermost on a flat surface and fixed found in all stools examined and we found that the in a modified Susa fixative. The dissecting micro- frequencies of positive stool examinations were scope appearances of the mucosa were recorded similar in the different patient groups irrespective (Booth et al., 1962) noting the observer's assessment of the presence or absence of malabsorption. Forty- ofthe most numerous form or forms ofvilli present- seven per cent of stools from patients with normal that is, finger shaped villi, approximately equal absorption contained cysts and 44% of stools from numbers of finger and leaf shaped villi, etc. After subjects with severe malabsorption contained cysts paraffin embedding, 5 ,u sections of thejejunal biopsy of the parasite. In six patients (15%) the parasito- were cut and stained with haematoxylin and eosin. logical diagnosis was made only on examination of Histological appearances were assessed blind mucosal impression smears or jejunal aspirate. Three by one of us (D.S.R.) and graded according to a of these patients had severe diarrhoea and marked predetermined scale (normal or abnormal grades I malabsorption. to V), which is described in detail elsewhere (Ridley Three groups of patients designated M-0, M-1, and Ridley, 1976). The abnormalities in grade I and M-2 were defined. Eleven patients comprised were epithelial only, while grade V indicated sub- M-0 and all had normal intestinal absorption. Ten total villous atrophy. patients had impaired absorption of a single test http://gut.bmj.com/ After initial assessment patients were treated with substance (M-1) and 19 patients constituted the metronidazole 2-0 g as a single dose on three third group (M-2) who had malabsorption of two successive days (Khambatta, 1971; Petersen, 1972; or three substances. It is notable that three patients Green et al., 1974; Madanagopalan et al., 1975) or in the M-2 group had acquired the infection in mepacrine 100 mg, thrice daily for 10 days, or Africa, two were infected in the Middle East, and tetracycline 250 mg four times daily for four weeks. two were infected in Europe (Leningrad, USSR, and

In acute tropical sprue enterobacterial colonisation Italy respectively). Figure 1 shows the countries in on September 25, 2021 by guest. Protected copyright. of the jejunal mucosa has been described and treat- which subjects were infected. In one subject we were ment with tetracycline produced elimination of the able to estimate the incubation period to be five organisms and improvement in absorption (Tomkins days at the most before the onset of upper abdominal et al., 1975). If a similar state obtained in giardiasis discomfort, abdominal distension, nausea, and then similar responses to antibiotic therapy might diarrhoea. In the whole group diarrhoea, lassitude, be anticipated. The nature of this treatment was and abdominal distension were the most common explained to patients and their consent for it ob- symtoms at presentation (Fig. 2). These symptoms tained. Patients who received metronidazole were were more marked in the M-2 group than in M-0. advised to avoid alcohol for the duration of treat- Weight loss was prominent in the M-2 group. The ment because of its reported disulfiram-like actions median duration of symptoms was 17 weeks in (Taylor, 1964). At reassessment one to three months M-0 (range four to 104 weeks), 12 weeks in M-1 after treatment abnormal absorption tests were (range one to 260 weeks), and nine weeks in M-2 repeated, parasitological examinations were repeated, (range 12 days to 52 weeks). If M-2 subjects who and further jejunal biopsies were obtained. If malabsorbed all three substances are considered, parasites were still present further treatment was then this value is seven weeks (range 12 days to given with mepacrine or metronidazole and follow- 16 weeks). A few patients presented within days of up continued. their arrival in Britain but 11 of the M-2 category For comparison, we include results of similar had been here for over a month (Fig. 3). investigations from a group designated 'overland Despite the frequent occurrence of weight loss, controls' (OC) who did not have malabsorption the nutritional status of our patients was good. and a group of patients with untreated acute None had hypoproteinaemia or hypogamma- Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from

346 S. G. Wright, A. M. Tomkins, and D. S. Ridley

Per cent treated for an abdominal lymphoma with external radiotherapy four years before presentation to us. In this subject we found no evidence of an anaerobic microflora in the proximal jejunum. Malabsorption was present in 29 patients. Twenty- three malabsorbed D-xylose. Vitamin B12 absorption was abnormal in 20 patients and 15 had steatorrhoea (Fig. 4 and Table 1). The most severe abnormalities were present in the M-2 group. Mean stool weights were increased in the groups with malabsorption and the mean value in M-2 was significantly higher than in M-0 and M-1 (Table 2). Morphological abnormalities of the jejunal mucosa were common more marked histological Fig. 2 Symptoms at presentation to the Hospitalfor (Fig. 5a, b). In general, Tropical Diseases and their frequency in the three groups abnormalities were associated with more marked ofpatients. impairment of intestinal absorption. Significant

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224 - 3C .0 0 ) Faecal fat 2C .0 24- 0 /24 h C 0 0:. (q mvr- 0 * .1 t-.-* *4OC 20- C 0 Urinary 5 16- 0 excretion 58 IC 0 COVIT 0 0 B 12/24h 0 . 12 * 5 0 ~0. ~ ~ 0 0 )0 0 0 0 2C http://gut.bmj.com/ 8- 0 0 * 0 0 0 0 @ * 0 4- 0 2C @0 g0 0 0 0 0% D-xyloseDUrinary 4.C 0 0 excretion .00 ~ ~ ~ ~ ~ * M-0 M-1 M-2 (q/Sh) 6bc Fig. 3 Interval in weeks between arrival in Britain B8C andpresentation at the Hospitalfor Tropical Diseases 0~~~~~~~00 on September 25, 2021 by guest. Protected copyright. Mean for the three groups ofpatients with giardiasis. -*r .0 stool 401 0.. 2001- -t- . 0. globulinaemia. Selective IgA deficiency was not (q/24h) 0: 0. 0 .C. - found in any of those subjects examined. The O.C. M-0 M-1 M-2 T.S. mean serum folate was only slightly lower (4-6 ng/ml) in the M-2 group than the M-0 group Fig. 4 Absorption studies and stool weights in overland (6-0 ng/ml) but the mean serum vitamin B12 level control subjects (O.C.), patients with acute tropical was significantly lower in M-2 (mean ± SE = sprue (T.S.), and giardiasis patients before treatment. Interrupted lines indicate the lower or upper limit of 198 ± 94.5 pg/ml) than in M-0 (301 ± 32-3 pg/ml, P < 0-05). the normal range for each test as appropriate. and biochemical data o = normal Vitamin B12 absorption test; * = abnormal All other haematological Vitamin B12 absorption test (Chanarin 1969). were similar in the three groups. Barium follow- through examinations were performed in 35 patients. No evidence of anatomical or chronic inflammatory Table 1 Distribution of abnormal absorption tests in M-2 bowel lesions was found. These studies did show thickened mucosal folds and dilated loops of small Test substances malabsorbed No. ofpatients bowel in 25 subjects and normal appearances in D-xylose Fat Vitamin B1, 12 were 10 others. 14C-glycocholate breath tests normal D-xylose - Vitamin B12 5 in 13 of 14 patients. The single abnormal result was D-xylose Fat - 1 - Fat Vitamin B1, 1 obtained in a patient who had been successfully Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from

Giardiasis: clinical and therapeutic aspects 347 Table 2 Mean stool weights in three groups ofpatients Table 3 Number ofabnormal tests of intestinal absorption that returned to normal range after single Mean stool weight (g/24 h) course of medication shown M-O M-1 M-2 Medication Test of absorption 147 188 351 SEM 12-1 210 42-9 D-xylose Schilling test Faecalfat 113-846 Range 78-197 99-288 Metronidazole 5/9 6/9 5/6 Mepacrine 2/3 3/4 2/2 The mean value for M-2 was significantly higher than that for M-0 Tetracycline 0/6 2/4 0/4 (P < 0 005) and M-1 (p < 0 02).

IV. C. S C+R- ee R- 0* *e.e II- R+L CO A 7 ii- CO. * e0@ 50 CN L- C0 S. II L+F- 0 0 ae *0 x F- eeee *0 ** II- Iv. I ~~~~~~~~_ III. B II. ***@@ I, .e**.e S o@Se 00* Normal O.C. M-O M-1 M-2 rS. - II- N Fig. 5 A. The dominant form or forms of villi on dissecting microscopy ofjejunal biopsies at initial assessment: F = finger-shaped villi; L = leaf-shaped villi; R = ridge formations; C = convolutions. B. The 0 histological grading ofjejunal biopsies in A. http://gut.bmj.com/ enterobacterial colonisation of the jejunum was NX Pre Post Pr Post Post found in M-2 patients. These findings will be reported Metronidozole in detail elsewhere. It is notable that functional and Mepocrine Tetrocycline morphological abnormalities in M-2 giardiasis Fig. 6 Histological grading ofjejunal biopsies before and after treatment. patients were similar to patients with acute untreated on September 25, 2021 by guest. Protected copyright. tropical sprue (Figs. 4 and 5). Treatment was not allocated in a randomised way After tetracycline histological appearances often to similar groups of patients, so that differing re- deteriorated (Fig. 6). sponses cannot be compared statistically. A single course of metronidazole eradicated G. lamblia in Discussion 20 out of 22 patients (91 %). A second course of metronidazole increased the parasitological cure Though the pathogenicity of G. lamblia in man has rate to 95%. Mepacrine eradicated the parasite in been disputed (Palumbo et al., 1962), there is a sub- five out of eight patients (63 %). G. lamblia persisted stantial body of evidence which supports the role of in seven out of eight patients given tetracycline. the parasite in causing symptomatic disease in man. Intestinal absorption consistently improved in those Diarrhoea is the most common symptom in giardiasis. who took metronidazole or mepacrine and in Rendtorff (1954) showed in prison volunteers that Table 3 we show those abnormal absorption tests G. lamblia alone produced diarrhoea. Studies from which returned to the normal range. Changes in Asia have shown that the parasite is found much absorption after tetracycline were minimal in most more commonly in subjects with diarrhoea than in cases. Histologically, the effect of successful anti- asymptomatic ,subjects (Ingram et al., 1966; Antia giardial treatment was improvement in grading et al., 1966). Antia et al. (1966) showed further that (Fig. 6) with elimination of cellular infiltrate in the G. lamblia was present in only 5 5% of persons lamina propria and partial repair of the epithelial with miscellaneous gastrointestinal symptoms or in damage. Sequential biopsies from one patient 6-7 % of subjects with dysentery-that is, diarrhoea treatedwith metronidazole are shown in Figs. 7 and 8. with blood in the stools, a symptom not noted in Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from

348 S. G. Wright, A. M. Tomkins, and D. S. Ridley

Fig. 7 The pre-treatment biopsy in an M-2 subject (S.O.), showing marked grade II histological abnormality.

Fig. 8 Post-treatment (metronidazole) biopsy in patient S.O. showing improvement to minor grade I histological abnormality. http://gut.bmj.com/ giardiasis. These figures are very close to the pre- East, and one each in Italy and Leningrad. Mal- valence of4-4 % in asymptomatic carriers. In marked absorption associated with giardiasis has a wider contrast they reported a prevalence of 23-3 % in geographical distribution than tropical sprue, for subjects with non-dysenteric diarrhoea. Epidemic this entity has not been encountered in Africa giardiasis causing diarrhoea has been reported from (Cook, 1974). Though there is no specific feature Aspen, Colorado (Moore et al., 1969) and in groups which distinguishes tropical sprue, it usually of tourists USSR et visiting Leningrad, (Brodsky improves in response to a prolonged course of on September 25, 2021 by guest. Protected copyright. al., 1974). A persisting bowel upset that continues antibiotics, often with folate or vitamin B12 supple- for weeks or months is typical of giardiasis (Lancet, ments (Guerra et al., 1965; O'Brien and England, 1974), but this is not a feature of acute undifferenti- 1971; Rickles et al., 1972). Mepacrine, a commonly ated diarrhoea of the tropics. We found no evidence used anti-giardial drug, is known to have anti- of any other gut pathogen in our patients. bacterial actions in vitro (Seligman and Mandel, Malabsorption in giardiasis has been reported from 1971), but in the short courses used in the treatment a variety of geographical locations (Amini, 1963; of giardiasis (five to 10 days) it seems unlikely to Yardley et al., 1964; Antia et al., 1966; Alp and produce the same results as prolonged antibiotic Hislop, 1969; Moore et al., 1969; Tewari and treatment in tropical sprue. Tandon, 1974). The comparative paucity of reports Spontaneous recovery is known to occur in probably relates ,to the fact that giardiasis is most tropical sprue but this usually occurs when subjects common in countries where physicians' time and receive an adequate diet. Many of our subjects had hospital facilities cannot be expended on the study been in Europe or Britain and taking normal diets of an easily treatable gastrointestinal infection. A for weeks or months before presentation to us, by number of the studies noted above are from areas which time spontaneous resolution of tropical sprue in which tropical sprue is endemic and it might be would have occurred. Further giardiasis has been suggested that in these studies G. lamblia is a non- associated with malabsorption in non-immuno- pathogenic commensal. Just over half our total series deficient subjects who have acquired the infection of patients were infected in the Indian subcontinent in temperate climates (Yardley et al., 1964; Hoskins and South-East Asia, but, of seven M-2 subjects, et al., 1967; Morecki and Parker, 1967; Cain et al., three were infected in Africa, two in the Middle 1968; Moore et al., 1969) and in our patients visiting Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from Giardiasis: clinical and therapeutic aspects 349 Italy and Leningrad. Mepacrine in the former important. Disturbance of intestinal motility, subjects eradicated the parasite and absorption luminal competition by the parasite for substrates improved. (Ament, 1972), bacterial colonisation (Yardley and In our patients metronidazole eradicated the Bayless, 1967; Ament and Rubin, 1972; Tandon parasite and improvement in function and morpho- et al., 1974) and epithelial damage produced by the logy followed. This drug is known to be effective parasite (Morecki and Parker, 1967) have been against Entamoeba histolytica and Trichomonas suggested as contributory factors. The role of tissue vaginalis, both pathogenic protozoan parasites, invasion in producing malabsorption is difficult to and has anti-bacterial actions on obligate anaerobic assess for the reports of its occurrence are very few bacteria only (Garrod et al., 1973). Though anaerobic (Morecki and Parker, 1967; Brandborg et al., bacteria are associated with malabsorption in a 1967; Brandborg, 1971). Circulating antibody to number of clinical syndromes (Losowsky et al., G. lamblia in subjects with malabsorption (Ridley 1974), we found no evidence of anaerobic small and Ridley, 1976) may indicate either that mucosal bowel overgrowth from our bacteriological studies, invasion is much more common than we at present nor did we find any evidence of bile salt decon- appreciate or that this is only a marker of increased jugation as judged by negative 14C-glycocholate mucosal permeability with resultant absorption of breath tests. parasite antigen. Entamoeba histolytica is often The possibility that improvement in absorption harboured by asymptomatic individuals. Experi- after metronidazole is a non-specific effect of the mental work has shown that axenically cultured drug should be considered. In a series of eight amoebae must be associated with live bacteria for a immunodeficient subjects with malabsorption one minimum of 12 hours before invasive amoebiasis subject who did not harbour G. lamblia received can be produced in laboratory animals (Wittner metronidazole for several weeks without change in and Rosenbaum 1970). From our bacteriological absorption. In contrast, seven subjects who had studies we found evidence of enterobacterial con- proven giardiasis received metronidazole; the tamination of the jejunum in patients with marked parasite was eradicated in each case, jejunal mor- malabsorption, whereas no bacteria were present phology improved, and absorption returned to in subjects malabsorbing only one substance or with

normal (Ament and Rubin, 1972). Two subjects normal absorption. The possibility of synergism http://gut.bmj.com/ had received tetracycline before without effect and between enterobacteria and G. lamblia to cause one subject had required systemic steroids to keep damage to the intestinal mucosa cannot be excluded. him alive. After metronidazole his malabsorption In any subject who has a bowel upset that persists regressed, he put on weight and steroids were with- for weeks or months after an initial acute onset the drawn. It is notable that after treatment of giardiasis possibility of giardiasis should be considered, even in these subjects malabsorption regressed despite in subjects whose travels have been limited to Europe.

the presence of an abnormal small bowel flora at Single negative stool examinations are insufficient on September 25, 2021 by guest. Protected copyright. follow-up assessment. Morphological improvements to exclude the diagnosis and small intestinal aspira- were marked in these subjects who had multiple tion and biopsy may be necessary to demonstrate biopsies taken both before and after treatment. the parasite. The satisfactory therapeutic response From these findings it seems likely that in some to eradication of the G. lamblia with improvement patients G. lamblia can cause malabsorption. The in mucosal function and morphology suggests a circumstances in which this occurs are ill pathogenic role for this parasite but the mechanisms understood at present but do not seem to be en- await elucidation. tirely related to the presence of an abnormal small bowel flora. We are grateful to the pathology services of Univer- We found D-xylose and fat malabsorption to be sity College Hospital group for their invaluable common in the subjects we studied. The prevalence help in this study. of vitamin B12 malabsorption was very high (present in 50% of the whole group and 69% of those with References malabsorption). H. A. K. Rowland at this hospital Allen, A. V. H., and Ridley, D. S. (1970). Further observa- tions on the formol-ether concentration technique for (1974, unpublished) found a similar prevalence faecal parasites. Journal of Clinical Pathology, 23, 545-546. (67% of 55 patients). These results confirm the Alp, M. H., and Hislop, I. G. (1969). The effect of Giardia earlier but infrequent reports of malabsorption of lamnblia infestation on the gastrointestinal tract. Australian this vitamin in giardiasis (Antia et al., 1966; Ament Annals of Medicine, 18, 232-237. Ament, M. E., and Rubin, C. E. (1972). Relation of giardiasis and Rubin, 1972; Notis, 1972; Ament, 1972). to abnormal intestinal structure and function in gastro- The mechanisms of malabsorption in giardiasis intestinal immunodeficiency syndromes. Gastroenterology, remain obscure. The total parasite load may be 62, 216-226. Gut: first published as 10.1136/gut.18.5.343 on 1 May 1977. Downloaded from 350 S. G. Wright, A. M. Tomkins, and D. S. Ridley Ament, M. E. (1972). Giardiasis and vitamin B12 malabsorp- Livingstone: Edinburgh. tion. Gastroenterology, 63, 1085. Madanagopalan, N., Rao, U. P., Somasundaram, A., and Amini, F. (1963). Giardiasis and steatorrhoea. Journal of Lakshmipathi, T. (1975). A correlative study of duodenal Tropical and Medical Hygiene, 66, 190-192. aspirate and faeces examination in giardiasis before and Antia, F. P., Desai, H. G., Jeejeebhoy, K. N., Kane, M. P., after treatment with metronidazole. Current Medical and Borkar, A. V. (1966). Giardiasis in adults; incidence, Research Opinion, 3, 99-103. symptomatology and absorption studies. Indian Journal Moore, G. T., Cross, W. M., McGuire, D., Mollohan, C., of Medical Science, 20, 471-477. Gleason, N. N., Healy, G. R., and Newton, L. H. (1969). Booth, C. C., Stewart, J. S., Holmes, R., and Brackenbury, Epidemic giardiasis at a ski resort. New England Journal W. (1962). Dissecting Microscope Appearances ofIntestinal of Medicine, 281, 402-407. Mucosa, p. 2. Ciba Foundation Study Group. No. 14. Morecki, R., and Parker, J. G. (1967). Ultrastructural studies Churchill: London. of the human Giardia lamblia and subjacent jejunal mucosa Brady, P. G., and Wolfe, J. C. (1974). Waterborne giardiasis. in a subject with steatorrhea. Gastroenterology, 52, 151- Annals of Internal Medicine, 81, 498-499. 164. Brandborg, L. L. (1971). Structure and function of the small Notis, W. M. (1972). Giardiasis and vitamin B12 malabsorp- bowel in some parasite diseases. American Journal of tion. Gastroenterology, 63, 1085. Clinical Nutrition, 24, 124-132. O'Brien, W., and England, N. W. J. (1971). Tropical Sprue Brandborg, L. L., Tankersley, C. B., Gottlieb, S., Barancik, and Megaloblastic Anaemia, pp. 48-59. Wellcome Trust M., and Sartor, V. E. (1967). Histological demonstration Collaborative Study. 1961-1969. Churchill Livingstone: of mucosal invasion by Giardia lamblia in man. Gastro- Edinburgh. enterology, 52, 143-150. Palumbo, P. J., Scudamore, H. N., and Thompson, J. H. Brodsky, R. E., Spencer, H. C., and Schultz, M. G. (1974). Jr (1962). Relationship of infestation with Giardia lamblia Giardiasis in American travellers to the Soviet Union. to intestinal malabsorption syndromes. Proceedings Journ.al of Infectious Diseases, 130, 319-323. of the Staff Meetings of Mayo Clinic, 37, 589-598. Cain, G. D., Moore, P., and Patterson, M. (1968). Mal- Petersen, H. (1972). Giardiasis (Lambliasis). Scandinavian absorption associated with Giardia lamblia infestation. 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