Clinical aspects of Giardia infection in dogs

This article reviews the clinical aspects of Giardia intestinalis infection in dogs based on its author's experiences. The Giardia intestinalis infection is critical to dogs and humans since the protozoa induce the digestive tract disorders. Moreover, the potential of zoonotic transmission from dogs to humans is recognized, according to the genotype analysis of isolates in dogs and humans. No characteristic clinical features were observed in the author's research. Only 13.4% cases showed that the diarrhea in the 171 cases of Giardia intestinalis infected dogs, and many remained cases were sub-clinical without diarrhea. The diagnosis of Giardia intestinalis infection is difficult because of its low sensitivity of convenient microscopic examination method. The infection of Giardia intestinalis in household dogs seems to be still underestimated today. The multiple examinations using the direct smear method and the cyst concentration method are recommended to detect Giardia in individual animal hospitals. The epidemiological backgrounds of dogs are very important to suspect Giardia intestinalis infection in household dogs. The detection of Giardia intestinalis specific antigen in private household dogs was high levels in dogs aged 1-6 month olds (22.8%, 83/364), and those derived from pet shops/breeding kennels (20.5%, 130/634). In addition, the cases of 83.5% (137/164) in Giardia antigen positive dogs were kept indoors. It is a serious problem for zoonotic transmission, because the infected dogs are much close contact with humans. The clinical cases of canine giardiasis were treated with nitromidazole (metronidazole tinidazole) and benzimidazole (febantel combination, albendazole, and febendazole). All of the agents were effective for canine giardiasis in Japan, since the fecal conditions were recovered and the shedding of cysts was eliminated. Especially, febendazole (50 mg/kg, once a day for 3 days) was recommended to control canine giardiasis because of its excellent efficacy and potential of antinematodes activity.