Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2006
Publication Date: 5/1/2007
Citation: Dubey, J.P., Huong, L.T., Sundar, N., Su, C. 2007. First isolation and genetic characterization of Toxoplasma gondii from tissues of dogs from Vietnam. Veterinary Parasitology. 146:347-351.
Interpretive Summary: Toxoplasma gondii is a single celled parasite of all warm blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. Scientists at the Beltsville Agricultural Research Center and an Univ. in Vietnam report first survey of T. gondii infection in dogs in Vietnam. The results will be of interest to biologists, parasitologists, and veterinarians.
Technical Abstract: Dogs are considered a potential risk for transmission of Toxoplasma gondii to humans because they can mechanically transmit oocysts to people and in certain parts of the world dog meat is consumed by humans. The prevalence of T. gondii in 42 unwanted dogs from Vietnam was determined. Antibodies to T. gondii were assayed by the modified agglutination test, and found in 21(50%) of 42 dogs with titers of 1:20 in six, 1: 40 in seven , 1: 80 in two, 1: 160 in two, 1:320 in two, 1 : 640 in one, and 1:1280 or higher in one. Hearts, tongues and brains of 21 seropositive dogs were bioassayed in cats, mice or both. Tissues from eight seropositive dogs were fed to eight T. gondii free cats. Feces of cats were examined for oocysts. T. gondii was isolated from eight dogs by bioassay in cats. Genotyping of these eight T. gondii isolates using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22 8, c29 2, L358, PK1 and a new SAG2, and an apicoplast marker Apico revealed two genotypes. Both genotypes are different from the predominant type I, II and III lineages that are widely spread in North America and Europe. This is the first report of isolation of viable T. gondii from any host in Vietnam.