Cryptosporidium muris is particularly hazardous for people with suppressed immune systems from drugs or diseases, e.g. AIDS.
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Biomedical subjects
Publications and source records attributed to D Baxby.
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The development of clinical disease and the pathogenesis of cowpox were studied in domestic cats inoculated by a variety of routes. Intradermal titration in two cats demonstrated that as little as five pfu of cowpox virus caused a primary skin lesion. Intradermal inoculation of greater than or equal to 10(5) pfu cowpox virus resulted in severe systemic disease. Large amounts of virus (greater than or equal to 10(3) pfu/g) were isolated from skin lesions and the turbinates of cats killed at eight and 11 days post-inoculation (dpi). Lesser amounts of virus (congruent to 10(2) pfu/g) were isolated from lymphoid tissues and the lung, and small amounts of virus were isolated from various other tissues. A white cell-associated viraemia was detected from 5 dpi onwards. Skin scarification with 10(3) or 50 pfu cowpox virus enabled reproduction of the naturally-acquired disease. Cat-to-cat transmission was demonstrated from cats inoculated by skin scarification, but caused only subclinical infection in sentinel cats. Oronasal inoculation resulted in transient coryza and milder generalized disease than skin inoculation, and no transmission to sentinel cats. Preliminary investigations showed vaccinia virus (Lister strain) to be of low infectivity in cats while inoculation of ectromelia virus (Mill Hill strain) did not cause any clinical signs.
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Feces from some patients with clinically unremarkable cryptosporidiosis contained an unusual variety of oocyst not previously recognized. These atypical oocysts were shown by electron microscopy to have a distinctive three-layered outer coat and, by immunofluorescence with a monoclonal antiserum, to lack an antigen present on the surface of typical oocysts. In contrast to typical oocysts, the atypical variety is very fragile and quickly collapses when suspended in solutions of high osmotic pressure or in lipid solvents. Atypical oocysts cannot be stained by methods used to stain typical oocysts, but their appearance in sucrose-phenol is characteristic. Their stability in this solution, though much less than that of typical oocysts, is sufficient for them to be recognized and for cases to be diagnosed by microscopy. Patients who excreted atypical oocysts never excreted the typical variety. General findings in patients who excreted atypical oocysts were no different from those who excreted typical oocysts.
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Little is known of the ways in which orthopoxviruses are maintained in nature, and the role of wild-life reservoirs requires further investigation. This lack of information is important in view of proposals to use as vaccines recombinant vaccinia viruses which carry genes for other immunising antigens. The possibility that such strains may become established in nature, as vaccinia may have in Indian buffaloes, and/or undergo genetic hybridisation with existing orthopoxviruses should be considered.
The clinical findings from 30 cases of feline poxvirus infection in the UK are reviewed and some epidemiological observations described and discussed. In most cases the clinical signs consisted of skin lesions only, although systemic signs were also occasionally seen. Over half the cats had a history of a single recent lesion, assumed to be primary, on the head, neck or a forelimb. Twenty-nine of 30 cats developed more widespread secondary skin lesions. Cat-to-cat transmission was apparently rare. More cases were recognised in the autumn than at other times of the year. The possibility of a wild mammal reservoir of infection is discussed.
A two-year prospective survey of patients with diarrhoea at a children's hospital detected 65 cases of cryptosporidiosis; 56 were index cases representing 1.4% of patients examined. There was a marked seasonal variation with fewer index cases in July-September (0.4-0.6%) than February-April (3-5%). All four adult cases were contacts of infected children and 21 (32%) of the patients were 12 months old or younger. Cryptosporidium was the fourth commonest diagnosed cause of gastroenteritis, the second most common non-viral cause, was responsible for 7.2% of all cases, and 14.7% of non-viral cases where a cause was identified. As such it should be sought routinely in cases of gastroenteritis in children.
Stool samples from 83 Sudanese children with gastro-enteritis were examined using a safranin-methylene blue stain. Five children (6.1%) were excreting cryptosporidium oocysts but no other potential enteropathogens. The clinical features of anorexia, vomiting and pyrexia and the profuse green watery offensive stool were similar to those reported previously. All of the children were dehydrated. None of 37 children studied who did not have gastro-enteritis was excreting oocysts.
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Studies were made on 33 immunocompetent patients with cryptosporidiosis (31 of them children) to determine how long oocyst shedding continued after the cessation of diarrhoea. The majority (20/33) ceased to shed oocysts in the week following the cessation of diarrhoea. However 5 patients (15%) continued to shed oocysts for 2 weeks or more, and 1 patient was still shedding oocysts when lost to follow-up 3 weeks after the diarrhoea ceased. There was considerable variation among patients, and some eliminated oocysts more efficiently and quickly than others. The sucrose flotation technique was more useful than direct smear for detecting the low numbers present at the end of the shedding period. Limited information suggested that a carrier state or relapse is probably rare.
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We describe a case of recurring cryptosporidiosis during immunosuppressive treatment. The infection occurred after contact with an affected kitten and followed a less severe course than expected. After withdrawal of immunosuppressive treatment the infection resolved.