In vitro embryonation of Syphacia obvelata eggs

Mouse infections with the pinworm, Syphacia obvelata, were evaluated as a potential model of human enterobiasis. Eggs of S. obvelata were found to be much less resistant to adverse environmental factors than those of Enterobius vermicularis, perishing rapidly when exposed to desiccation or to water. The average number of eggs produced by a female worm was 317 +/- 29 S.D. (range: 266-347), which is about 2-3% of the fecundity of E. vermicularis. Eggs expressed from gravid S. obvelata were incubated under various conditions, but the only reliable method of supporting complete embryonation was culture on a floating cellophane membrane. At 30 degrees C on this substrate, eggs were found to be infective between 6 and 42 h, inclusive. The pre-patent period in mice fed these eggs was 11-15 days. The more fastidious developmental and survival requirements of Syphacia eggs indicate that transmission of this species depends on much more intimate contact between hosts than is required by E. vermicularis.

Diagnosis by faecal culture of Dientamoeba fragilis infections in Australian patients with diarrhoea

This paper reports the first survey in Australia to use faecal culture to detect Dientamoeba fragilis in patients with diarrhoea. Of 3 different protozoal culture media evaluated on a case of known infection, modified Boeck & Drbohlav's medium was the most suitable. The organism could be grown from faeces stored for up to 24 h at room temperature, but for only 10 h at 4 degrees C. Culture was then used, in combination with microscopy of smears fixed with polyvinyl alcohol and trichrome-stained, to examine single stool specimens from 260 consecutive patients with diarrhoea in the city of Brisbane. D. fragilis was detected in 4 (1.5%) specimens, only 2 of which were positive by microscopy. Other protozoa were found in 36 (13.8%) specimens: Blastocystis hominis in 28 (10.8%), Giardia duodenalis in 4 (1.5%), Endolimax nana in 3 (1.2%), and Entamoeba coli in one (0.4%). One strain of Dientamoeba was cryopreserved in liquid nitrogen and recultured successfully 10 d later. Culture was more sensitive than microscopy in diagnosing D. fragilis infection and the organism, of dubious pathogenicity, was not common in patients with diarrhoea in this community. Prevalence surveys of intestinal protozoan infections should use faecal culture, and specimens should be less than 12 h old and not refrigerated. Dientamoeba strains isolated by culture can be cryopreserved.

Observations on strongyloidiasis in Queensland aboriginal communities

OBJECTIVE

To report the prevalence and distribution of infections with the parasitic nematode Strongyloides stercoralis in the Aboriginal and Torres Strait Islander communities of Queensland.

DESIGN

A 20-year retrospective survey of computerised data and selected files from the former Aboriginal Health Programme (AHP) of the State Health Department of Queensland, based on cases diagnosed by the microscopic examination of preserved faecal specimens. Findings were compared with figures published in annual reports.

STUDY POPULATION

Children under 15 years of age from 122 Aboriginal and Torres Strait Islander communities.

RESULTS

Numbers of specimens examined varied widely according to time and place, as did detected infection rates. In 32,145 faecal samples examined by AHP microscopists during 1972-1991 the overall infection prevalence was 1.97%. Strongyloides larvae were found in only 52 of 122 communities. The parasite was absent from many small, southern inland communities, and the prevalence of infection increased in northern regions with summer wet seasons. On average, it was highest in Doomadgee (12%), where a peak prevalence of 27.5% (92/334 children examined) was detected in a wet season survey. Some infections resolved spontaneously, while others persisted for more than four years. At Gununa (Mornington Island), the prevalence fell from 26.2% to below 7% after thiabendazole treatment of most infected children, and remained at this level for at least four years. Single stool examinations by experienced microscopists may have failed to diagnose at least 26% of infected cases. The records give no indication of the clinical impact of strongyloidiasis.

CONCLUSIONS

Strongyloidiasis is well established in many Aboriginal communities of north-eastern Australia. Children appear to be the major reservoirs of infection; the prevalence in adults is probably much lower. Failing improvements in community sanitation and hygiene, it may be possible to reduce significantly, if not eradicate, the infection by selectively treating diagnosed children with thiabendazole.

Detection of antibodies to secretions of Ancylostoma caninum in human eosinophilic enteritis

To evaluate the role of canine hookworms in human eosinophilic enteritis (EE) in north-eastern Australia, we tested human sera in an enzyme-linked immunosorbent assay (ELISA) which incorporated antigens of adult Ancylostoma caninum. Sera from the following groups were examined: 10 patients with EE (unexplained recurrent abdominal pain and related symptoms, with peripheral eosinophilia) from Townsville and Brisbane; 2 persons known to be infected with A. caninum and 20 presumed unexposed healthy controls; 20 patients with other gastrointestinal diseases; 20 with other identified parasitic infections; and 20 with atopic conditions. High levels of specific immunoglobulin (Ig) G and IgE antibodies were found in patients with EE but not other gastrointestinal disease. Excretory-secretory (ES) products were more discriminating than somatic antigens in the ELISA and the IgG/ES-ELISA was the most specific; occasional cross-reactions could be explained on epidemiological or parasitological grounds. The IgM-ELISA was neither specific nor sensitive. We conclude that canine ancylostomiasis is a major cause of human EE in north-eastern Australia, and the pathogenesis is based probably on hypersensitivity to antigens secreted by the parasite.

Successful treatment of disseminated strongyloidiasis

OBJECTIVE

To report the successful treatment of Strongyloides stercoralis hyperinfection, which is usually lethal but in this case was diagnosed in its early stages.

CLINICAL FEATURES

A 44-year-old woman, who had spent much of her life in Fiji and India, was treated with a high dose of prednisolone for rheumatoid arthritis complicated by gold lung. The onset of abdominal symptoms, an exacerbation of respiratory symptoms, and a persistent high eosinophil count and serum IgE level, led to the detection of numerous Strongyloides larvae in her faeces and sputum.

INTERVENTION AND OUTCOME

She was treated with thiabendazole for five days, then mebendazole for one month, and the dose of prednisolone was reduced. Clinical symptoms and signs improved within days and after one week parasites could not be found in her faeces. After six months, enzyme-linked immunosorbent assay for Strongyloides infection gave a reading which was 40% of the initial level but still in the positive range.

CONCLUSION

Steroid therapy in individuals with chronic, subclinical strongyloidiasis predisposes to the insidious development of hyperinfection syndrome, which has a high mortality rate. If detected early, this complication can be treated effectively. It can be prevented by actively seeking Strongyloides infection, by faecal microscopy and culture techniques and by serological tests, in high-risk individuals, such as immigrants from endemic areas.

Intestinal parasites in Zambian patients with AIDS

Previous studies have found a high prevalence of Isospora belli and Cryptosporidium parvum infections in African acquired immune deficiency syndrome (AIDS) patients with chronic diarrhoea. We aimed to determine the prevalence of gastrointestinal parasite in AIDS patients in hospital, not only those with diarrhoea, and to compare them with the general community. Clinically diagnosed AIDS patients in a Zambian teaching hospital were interviewed and examined, and stool specimens were studied for parasite infection. A control group was recruited from adults in a township near Lusaka. Of 90 AIDS patients (58% male), 50 (56%) had chronic diarrhoea and 9 (10%) had diarrhoea of shorter duration. In the control group (105 adults; 85% female), only one complained of diarrhoea. A variety of intestinal protozoa and helminths was found in 57% of AIDS patients and 88% of the community members. Isosporiasis was detected in 7, and cryptosporidiosis in 2, AIDS patients, all with diarrhoea, but not in any control. Strongyloides was found in 2 AIDS patients with diarrhoea and one community resident. Hospital patients with AIDS had fewer Entamoeba coli and E. histolytica infections, probably because of previous chemotherapy. We conclude that AIDS predisposes to isosporiasis and cryptosporidiosis, but not to infection with extracellular intestinal parasites, such as Entamoeba species, Blastocystis, Chilomastix, Endolimax, Ascaris and Necator.

Human ectopic fascioliasis in Australia: first case reports

OBJECTIVE

To describe the manifestations of two cases of migratory ectopic fascioliasis diagnosed in Australia, including the first report of lymphatic infection.

PRESENTATION

Both patients presented with acute, superficial swellings. In the first, a 46-year-old woman, the lump was found to be a cervical lymph node containing a mature Fasciola hepatica which had released eggs into surrounding tissues. The second patient was a 34-year-old male abattoir worker, in whom the subcutaneous lesion resembled an infected sebaceous cyst and contained an immature fluke.

FINDINGS

Both lesions were resected and diagnosed histologically. Fasciola eggs were not found in the faeces of either patient. Blood eosinophilia was not detected in either case. A serological test for fascioliasis was carried out in the second case and the result was positive. In both cases, infection was probably acquired in Australia, although neither patient had eaten watercress.

OUTCOME

Neither patient was specifically treated with anthelminthic agents, and neither suffered further complications.

CONCLUSION

Migratory fascioliasis occurs in Australia. It can present as superficial or deep focal lesions, not necessarily in association with peripheral blood eosinophilia or Fasciola eggs in faeces. Serological tests may be helpful in diagnosing such cases.

Isosporiasis in the aboriginal population of Queensland

OBJECTIVE

To report on the endemicity of Isospora belli in Queensland.

DESIGN

A 10-year retrospective survey of data from routine parasitological surveillance of Queensland Aboriginal communities, by microscopic examination of preserved faecal specimens.

SETTING

The Aboriginal Health Programme of the Queensland Department of Health and Medical Services.

POPULATION

Children under 15 years of age from all the Aboriginal communities of Queensland.

RESULTS

Oocysts of I. belli were detected in 33 (0.2%) of a total of 17,642 faecal samples examined.

CONCLUSION

Isosporiasis is endemic in the Queensland Aboriginal population. It is likely to be more common than indicated, because the infection is difficult to diagnose, and the techniques used to identify the organism were not particularly sensitive. It is predicted that isosporiasis will be recognised with increasing frequency as a cause of diarrhoea in Aboriginal and white Australians who develop AIDS.

Strongyloidiasis in North Queensland: re-emergence of a forgotten risk group?

OBJECTIVE

To describe the clinical presentation, diagnosis and management of strongyloidiasis in northern Queensland, and to identify predisposing factors for this infection.

DESIGN

A five-year retrospective study of medical records of all cases diagnosed in a regional hospital microbiology laboratory, with follow-up by interview where possible.

SETTING

The Townsville General Hospital.

PATIENTS

A total of 14 cases of strongyloidiasis were identified, with patients ranging in age from 7 months to 59 years.

RESULTS

Infected patients included nine Aborigines and two Vietnamese refugees, both high-risk groups. Of three Caucasians diagnosed, one was a war veteran, but the other two did not have significant travel histories; all three had lived or worked under insanitary conditions. In only one case was strongyloidiasis suspected; in most, it was diagnosed because of diarrhoea or blood eosinophilia which could not be related to the presenting illness. Thiabendazole treatment was effective in most cases.

CONCLUSION

In northern Australia, strongyloidiasis can be acquired locally by Caucasians who live in unhygienic circumstances. It should be suspected in any person with unexplained abdominal pain, diarrhoea, cutaneous symptoms or blood eosinophilia, and the laboratory must be informed of the provisional diagnosis.

Unidentified trematode eggs in faeces of Australian aboriginal children

In routine surveys for intestinal parasites among Aboriginal/Torres Strait Islander populations, eggs of unidentified trematode species have been found in the faeces of three children. In two of these, the eggs appeared to belong to a schistosome, or perhaps monogenean, species, and in the third, they were most likely from a monostome of dugongs. Although these probably represent cases of spurious parasitism, one or more may have been a true infection.

Observations on the morphology of Toxocara pteropodis eggs

Fertile eggs of Toxocara pteropodis, passed in the faeces of juvenile flying-foxes, were ovoid to spheroid in shape with a diameter range of 80-110 microns. The shell was often seen to comprise 4 layers: a fine inner lipid layer, a thicker clear chitinous layer, an equally thick outer vitelline layer and a pitted outermost, proteinaceous uterine layer of variable thickness. Infertile eggs were less uniform in shape and generally did not have well-defined shell layers, the formation of which is triggered by sperm penetration of the oocyte. The eggs of this species are bulkier than those of related ascaridoids, apparently because of a thicker external coat which, while not providing mechanical strength, is thought to protect against desiccation. Scanning electron microscopical findings suggest that the outer layer is not applied directly by uterine cells, but forms by the gradual deposition of secretions in the uterine lumen, regardless of whether the oocyte has been fertilized.

Eosinophilic enteritis presenting as surgical emergencies: a report of six cases

Eosinophilic enteritis is now commonly diagnosed in northern Queensland, and cases have been seen elsewhere. The patients present with acute abdominal symptoms, which may mimic appendicitis, and many cases are managed by surgery. To facilitate the diagnosis of this unusual syndrome, six surgically treated cases are reported here. Blood eosinophilia may be a helpful diagnostic feature, but in some cases it does not develop until after the acute abdominal episode. Most cases resolve satisfactorily with conservative management.

Aberrant migration by Toxocara pteropodis in flying-foxes--two case reports

Adults of the large nematode, Toxocara pteropodis, have not previously been reported from extra-intestinal sites in their hosts, juvenile flying-foxes (fruit-bats of the genus Pteropus). In one captive bat which died unexpectedly, a nematode was found coiled within the gall bladder and common bile duct; in another a nematode was in the esophagus and protruded into the laryngopharynx. Like other ascaridoids, this species is capable of aberrant migration.

Human eosinophilic enteritis caused by dog hookworm Ancylostoma caninum

An epidemic of eosinophilic enteritis (93 cases) has occurred in Townsville, northern Queensland, Australia. A hookworm was found attached to a resected, inflamed ileal segment from 1 patient but the species could not be identified. An adult hookworm of species Ancylostoma caninum was recovered at colonoscopy from the terminal ileum of a later patient. All of 38 patients interviewed in an epidemiological survey described behaviour which could have exposed them to infective larvae of this widespread dog parasite.