An infection by Giardia duodenalis is called giardiasis. Giardia spp are protozoan parasites which can spread through water sources and exist in damp environments. Once consumed, the Giardia spp protozoa attaches onto the lining of the intestines, absorbing nutrients and multiplying.
Transmission
Transmission is faecal-oral and so is usually passed through food or water contaminated by faeces of infected animals or through direct contact with the animals themselves.
The infective cyst stage can survive in the environment for several weeks and only a low number of cysts need to be consumed to produce an infection. Therefore, when there are a few infected animals, infection spreads quickly and can produce incidences of 100% in some cases.
Clinical signs
Signs are most commonly seen in young animals and include: weight loss, stunted growth, inappetance, chronic diarrhoea and sometimes vomiting.
Diarrhoea is usually soft, malformed, pale, smelly and may appear fatty. It doesn’t normally contain blood or mucus.
Diagnosis
Faecal smears. Examining fresh faeces under a microscope can show motile juvenile forms of Giardia spp (trophozoites).
Faecal flotation. Giardia spp cysts can be found in faecal samples using faecal flotation (see diagnostics section).
Advanced laboratory tests. Faecal samples can be sent off to a laboratory for testing using ELISA or PCR methodology.
False negatives for Giardia spp are common, so before ruling out an infection with this protozoa, 3 faecal examinations over 7-20 days should be performed.
Treatment
Giardia spp infections can be very difficult to treat due to environmental re-infection. Therefore, alongside individual animal treatment, environmental control should be conducted to eliminate Giardia spp cysts. Ammonium-based compounds have shown efficacy in inactivating cysts in the environment.
Infected animals should also be bathed to remove any cysts from the fur.
Individual animal treatments can include:
- Fenbendazole (50mg/kg per day for 5-10 days)
- Albendazole (25mg/kg per day for 4 days)
- Metronidazole (25mg/kg twice daily for 5 days). Side effects can include anorexia and vomiting, so the use of this drug should be secondary to fenbendazole.
Due to the high risk of infection through environmental contamination, treatment of non-symptomatic animals who share the infected dog’s environment should be considered.
Prevention
Giardia spp cysts can infect other animals as soon as they are passed in faeces. Therefore, collection of faeces from the environment swiftly is essential to reduce the risk of environmental contamination. Shelters, kennels and clinics should collect faeces routinely at least twice daily.
If Giardia spp are found and the animal has been on grass areas, consider these areas contaminated for at least 1 month.
Treatment of environments with ammonium compound substances inactivates the cysts, and for maximum efficacy these compounds should be left on surfaces for 5-20 minutes.
Prognosis
The prognosis is good in most cases if diagnosed and treated quickly. Young, very old or animals with comorbidities may be adversely affected more than healthy animals.