Atlas of livestock parasites
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Giardia spp.



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Protozoa (fagellate)

Giardia intestinalis (syn. G. duodenalis), G. lamblia, G. canis, G. cati.

The number and correct nomenclature of species are currently under investigation. Molecular analysis is now used to allocate isolates into assemblages.  Most isolates from dogs belong to assemblages C and D, and cat isolates fall into assemblage F.          

Distribution: Worldwide.   

Host: Small intestine of dogs, cats, many other animals, and humans. 

Life Cycle: Dogs and cats are infected by ingesting cysts in the environment. Trophozoites are stimulated under certain conditions to encyst and are passed from the host in feces.

Diagnosis: Examination of feces for cysts is the most sensitive microscopic technique. Cysts are best detected by 33% ZnSO4  centrifugal fotation; other fotation solutions often cause rapid           distortion. Motile trophozoites are occasionally seen in a direct saline smear of fresh diarrheic feces or may be in duodenoscopic aspirates (aspirates should be centrifuged and the sediment examined for       trophozoites). Trophozoites are likely to be dead and unrecognizable if fecal examination occurs longer than 30 minutes after sample collection or if the sample has been refrigerated.

Multiple fecal examinations (i.e., three exams done on samples collected over a 5- to 7-day period) may be necessary to rule out infection (a point of use fecal antigen test). Fecal enzyme-linked immunosorbent assay (ELISA) and indirect fuorescent antibody (IFA) tests are also available.

Size: 9–13 × 7–9 µm  Cyst            

Size: 12–17 × 7–10 µm Trophozoite   

Clinical features: Giardia is a common parasite of small animals. Many infections are asymptomatic, but Giardia may cause acute, chronic, or intermittent diarrhea, particularly in young dogs and cats. Since the role of pets in human Giardia infection is controversial, infections should be regarded as potentially zoonotic !   


Giardia spp. trofozoits
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Giardia spp. trofozoit
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Giardia spp. details of trophozoit
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Giardia spp. trophozoits
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