ABSTRACT
The frequency of Neospora spp., Leptospira spp. and Brucella abortus infections in adult cattle was determined in herds of the State of Pará, Brazil, which is an important region for cattle production located in the Amazon region. A total of 3466 adult female cattle from 176 herds were tested, leading to a frequency of seropositive animals of 14.7%, 3.7% and 65.5% and a herd positivity of 87.4%, 41.3% and 98.8% for infections caused by Neospora spp., B. abortus and Leptospira spp., respectively. The five most frequently diagnosed serologic responses to Leptospira spp. were those against serovars hardjo, wolfii, grippotyphosa, hebdomadis and shermani. The following associations were found: practice of artificial insemination, large farm size, large herd size, large number of dogs and high number of total abortions per year with the presence of antibodies against serovar hardjo; positive results to serovar grippotyphosa with the presence of dogs; inappropriate disposal of aborted foetuses with positivity to serovar hebdomadis. Serovar grippotyphosa was also associated with number of episodes of abortions. Neospora spp. positive herds were associated with episodes of abortion and B. abortus infection with the disposal of dead animals and aborted foetuses on pastures and with the use of artificial insemination. In conclusion, the high frequency of brucellosis, leptospirosis and neosporosis in the region may be a consequence of social, natural and raising conditions as: (i) climate conditions that favour the survival and spread of pathogens in the environment; (ii) farms located in regions bordering forest areas; (iii) farms in areas of difficult access to the veterinary service; (iv) extensive beef herds raised at pastures with different age and productive groups inter-mingled; and (v) minimal concerns regarding hygiene practices and disease prevention measures.