Seroprevalence and incidence of Toxoplasma gondii and Neospora caninum infection in naturally exposed domestic dogs from a rural area of São Paulo state, Brazil

Abstract Dogs are hosts of the protozoans Toxoplasma gondii, which causes an important public health disease, and Neospora caninum. Studies that have evaluated toxoplasmosis and neosporosis for prolonged periods in dog populations are rare. We analyzed infection by both parasites in a domestic dog population over three consecutive years in São Paulo state, Brazil. In the 1st, 2nd and 3rd years of collection, 181, 193 and 172 domiciles were visited, and blood samples of 331, 371 and 348 dogs were collected for antibody serology, respectively. The seroprevalence of T. gondii in each year was 27.2%, 22.5% and 43.9%, respectively, and that of N. caninum was 7.8%, 4.8% and 6.8%, respectively. The incidence rates for T. gondii in the 2nd and 3rd collections were 13.2% and 30.0%, and those for N. caninum were 3.3% and 4.4%, respectively. Positive and negative serological conversions for both agents occurred at high frequencies during the study period. This study reveals the canine population’s serological profile and demonstrates the constant exposure of dogs to the investigated pathogens, indicating the need for prevention and control measures in the region.

摘要 犬是弓形虫（Toxoplasma gondii）与新孢子虫（Neospora caninum）两种原虫的宿主，其中弓形虫可引发一类重要的公共卫生疾病。针对犬群中长期开展弓形虫病与新孢子虫病相关研究的案例较为罕见。本研究针对巴西圣保罗州连续三年的家犬群体，分析两种寄生虫的感染情况。在研究的第1、2、3年，分别走访181、193和172户养犬家庭，共采集331、371和348只家犬的血液样本用于抗体血清学检测。各年度家犬群体中，弓形虫的血清阳性率依次为27.2%、22.5%与43.9%，新孢子虫的血清阳性率依次为7.8%、4.8%与6.8%。第二次与第三次采样期间，弓形虫的感染发生率分别为13.2%和30.0%，新孢子虫的感染发生率分别为3.3%和4.4%。研究期间，两种病原体的血清学阳转与阴转事件均以较高频率发生。本研究明确了该地区家犬群体的血清学流行特征，证实犬群持续暴露于目标病原体，提示该区域需采取针对性的预防与防控措施。