(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 zoonotic.

Parasite: Cryptosporidium canis, Cryptosporidium parvum
Common name: Cryptosporidium
Host: Dogs, livestock, humans
Pre-patent period: 2-14  days
Location of adults: Small intestine
Distribution: Worldwide
Transmission route: Oral (ingestion of oocysts directly or via contaminated food and water)
Zoonotic: Yes



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.


Oocysts are challenging to identify (Fig 1). 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. B. K. Linh)
Figure 2 Cryptosporidium oocyst stained using modified acid-fast staining. (Image credit: Dr. B. K. Linh)


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


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.