DOGS ARE DEFINITIVE HOSTS OF NEOSPORA-CANINUM

Dogs were investigated to determine if they are definitive hosts of Ne ospora caninum. Four dogs were fed N. caninum tissue cysts in infected mouse tissue, and two negative control dogs were fed uninfected mouse tissue. Dog faeces wa:re examined daily for 30 days using a sucrose f lotation technique. Three challenged dogs shed spherical to subspheric al unsporulated oocysts, measuring 10 to 11 mu m in diameter. Oocysts sporulated within 3 days and contained two sporocysts. each with four sporozoites. Outbred, inbred, and gamma-interferon knockout mice were inoculated with canine faecal extracts and monitored for evidence of n eosporosis using a variety of morphologic, immunohistologic, serologic , and genetic analyses. Mice that received faeces from each dog observ ed to shed oocysts were demonstrated to have neosporosis by two or mor e techniques, One mouse was demonstrated to be infected with N. caninu m by immunohistochemistry, ultrastructural analysis, and a species-spe cific PCR test. No evidence of neosporosis was observed in control ani mals. Based on this study, dogs are a definitive host of Neospora cani num. (C) 1998 Australian Society for Parasitology. Published by Elsevi er Science Ltd. All rights reserved.