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Parasitology 169

caninum occurs worldwide. Oocysts are passed material is relatively easy. An infected animal may
in dog faeces from 8–23 days after infection. show no clinical signs if the infection is light but
In cattle, infection may result in abortion, concurrent disease or environmental stress may
this is usually observed at 5–6 month gesta- tip the balance resulting in rapid build-up of infec-
tion although it can occur any time between 3 tive organisms and the development of diarrhoea,
months and full term. Abortions may be spo- dehydration and other complications. There are
radic or clustered. Foetuses can be born alive 26 valid species of Cryptosporidium reported of
(often underweight and with neurological signs) which not all are zoonotic. Some that are of zoo-
or they may die in utero in which case they often notic potential includes, C. parvum, C. meleagridis,
undergo mummification. C. ubiquitum, C. muris, C. canis, C. felis, and so on.

Diagnosis Diagnosis
Diagnosis is confirmed based on histological 1 Floating fresh faecal samples on 1.33 SpG
examination of freshly aborted foetuses. There sugar solution and examining under medium
are also serological tests; IFA and ELISA avail- and high power (20× and 40×) would help.
able (see Chapter 6). Cows infected with N. It appears with a pinkish tinge specifically on
caninum are likely to infect more than 95% of sugar float. The organism floats just beneath
their calves transplacentally. the coverslip and so on a plane of focus
slightly above than where we usually expect
parasites stages to be seen.
Prevention and control
2 Examination of fixed, Giemsa stained faecal
Prevention and control require efficient disposal smears. Owing to the fact that the organ-
of any aborted material to prevent dogs gaining isms are very small it is necessary to gain
access to potential sources of infection and also some familiarity with the appearance of the
ensuring that dog faeces does not contaminate stained organism to be confident of identify-
areas where cattle feed. ing Cryptosporidia in samples.
3 Phase contrast microscopy may be helpful for
examination of fresh specimens.
cryptosporidiosis 4 Antigen capture ELISA (see Chapter 6).

Cryptosporidium sp. are very small (4–8 µm diam- Prevention and control
eter) organisms that are often associated with
diarrhoea in young or debilitated animals. They 1 Hygiene and good management.
are now considered to be gregarines rather than 2 Control concurrent disease(s).
true coccidia, this may explain their refractoriness
to commonly used coccidiostats. The organisms
undergo schizogony, gametogony and sporogony trypanosomosis and leishmanosis
in vacuoles formed in the epithelial cells lining
the intestinal, and sometimes the respiratory Trypanosoma sp. (Figure 3.35) and Leishmania sp.
tract, renal epithelium and gallbladder. Cross are broadly classified as ‘flagellates’ due to many
infection among a wide range of vertebrate hosts of their life stages possessing flagella that allow
is common and auto-infection by ingestion of effective motility. Trypanosomes are transmitted
food contaminated with an animal’s own faecal by biting/blood-sucking insects (for example,

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