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The clinical features found in 14 children with toxocara ELISA titres of greater than or equal to 0.7 were compared with those found in 34 toxocara negative children. Blood eosinophils were elevated in 7 of the 14 patients and the highest eosinophilia was 14%. There was a highly significant association between hepatomegaly, cough, sleep disturbance and a raised titre (p less than 0.01). Behaviour disturbance, abdominal pain and headache were also significantly associated with a raised titre (p less than 0.05). The combination of abdominal pain, headache and cough was even more significantly associated with a high titre (p less than 0.0005) than were individual clinical features. It is suggested that in addition to the two well recognised clinical conditions of visceral larva migrans and ocular toxocariasis the clinical entity of covert toxocariasis should receive recognition. Eosinophilia may or may not be present in this condition.

An outbreak of waterborne cryptosporidiosis affecting 27 persons, diagnosed stool positive, occurred in Ayrshire in April 1988. Twenty-one in 27 confirmed cases required some form of fluid replacement therapy. Local general practitioners indicated a two- to fivefold increase in diarrhoeal disease during the outbreak, and following enquiries made by Environmental Health Officers it became apparent that many hundreds of people had suffered a diarrhoeal illness at that time. Cryptosporidium spp. oocysts were detected in the treated chlorinated water supply system, in the absence of faecal bacterial indicators. Oocyst contamination of a break-pressure tank containing final water for distribution was the cause of this waterborne outbreak. An irregular seepage of oocyst-containing water, which increased during heavy rains, was the cause of the break-pressure tank contamination, rather than a failure of the water-treatment processes. The waterborne route should be considered when clusters of cryptosporidiosis-associated with potable water occur. Waterborne cryptosporidiosis can occur in the absence of other faecal indicators of contamination.

Seven different flotation fluids were assessed for their efficiency in recovering Toxocara canis ova from artificially seeded soil samples. Using the most efficient (a saturated solution of magnesium sulphate plus 5% potassium iodide) 25 g amounts of 234 environmental soil samples were examined for the presence of Toxocara spp. and Toxascaris ova. Twenty-six samples (11.1%) yielded ova of one or other species. There was no discernible pattern of distribution of positives with relation to the source of the samples. The maximum number of ova recovered in any one sample was 19. All the ova recovered from the environment were considered viable and potentially infective.

Cryptosporidium parvum and Giardia duodenalis can cause severe diarrhoea in infected individuals and their transmissive stages, oocysts and cysts, are voided in large numbers with the faeces of infected hosts. Contaminated sewage effluents are recognised as a potential source of waterborne (oo)cysts. In this investigation methods optimised for the recovery of both from a range of wastewaters were used to determine the occurrence of these organisms in influents, effluents and sludges from seven sewage treatment works in England. The data indicated the presence of small numbers of oocysts both in sewage influent and effluent samples whereas cysts were detected more frequently and at higher concentrations in both influents and effluents. Whilst sludge samples from 1/5 sites contained oocysts, cysts were detected from all five sites. These investigations indicate that discharge of sewage effluents into a watercourse, which may be used for potable water abstraction, can contaminate that watercourse with potentially infectious oocysts. In addition, the application of sludge to land can be responsible for contaminating watercourses with (oo)cysts following run-off or leaching.

SUMMARYSalmonella carriage in 5888 gulls sampled by cloacal lavage was found to be 7-8 %. Marked geographical and seasonal differences in carriage rates were found.These differences appeared to be associated with human population density and seasonal differences in the reported incidence of human salmonellosis. The maximum duration of salmonella excretion in 17 laboratory-maintained gulls was 4 days and the number of salmonellae excreted was never more than 170 per gram of faeces. On the basis of this study it is suggested that gulls are not important factors in the aetiology of human salmonellosis.

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