Cryptosporidium

(Cryptosporidium canis, Cryptosporidium parvum)

Cryptosporidium spp. are protozoa with a wide host-range. Transmission occurs by the faecal-oral route either directly or via contaminated food and water. Puppies are most susceptible to illness. Cryptosporidium is a zoonosis.

Parasite: Cryptosporidium canis, Cryptosporidium parvum
Common name: Cryptosporidiosis
Host: dogs, livestock, humans
Pre-patent period: 2-14  days
Location of adults: small intestine
Distribution: worldwide
Transmission route: ingestion of oocysts directly or via contaminated food and water
Zoonotic: Yes

Distribution

Worldwide.

Clinical signs

Infection with Cryptosporidium is often asymptomatic, especially in adult dogs. If clinical disease manifests, it is usually associated with young and immunosuppressed animals.  Cryptosporidiosis in dogs tends to manifest as an acute bout of water diarrhoea, which usually resolves in 7-10 days but may be chronic if the host is immunocompromised.

Diagnosis

Oocysts are challenging to identify (Fig1). Specialized stains such as the Ziehl-Neelsen or modified acid fast staining of direct faecal smears (SOP 6) reveal red or pink 5-6 µm oocysts (Fig 2). Commercial rapid immunodiagnostic coproantigen kits are useful in-house diagnosis. PCR-testing may be available through commercial laboratories.

Figure 1. Unstained Cryptosporidium oocyst on a faecal float. (Image credit: Dr Bui Khanh Linh.)
Figure 2. Cryptosporidium oocyst stained using modified acid fast staining. (Image credit: Dr Bui Khanh Linh)

Treatment

A number of off-label drugs and regimes, for example, using azithromycin, paramomycin, tylosin and nitazoxanide, have been used with some success for the resolution of cryptosporiosis-related diarrhoea, however, have not been supported with controlled studies. None of these regimes have proven to result in the elimination of oocyst excretion.

Control

For control options, refer to the General Considerations and Recommendations section.

Public health considerations

Zoonotic transmission of C. parvum may occur in healthy individuals, with the most common source being calves and other humans.  Rare cases of infection with C. canis have been reported in children or patients with immunosuppressive disorders.