SEASONAL INCIDENCE AND HEMOPARASITE INFECTION-RATES OF IXODID TICKS (ACARI, IXODIDAE) DETACHED FROM CATTLE IN COSTA-RICA

To determine the tick species hindering the cattle industry in Costa R ica and to assess infection rates of ticks with three important hemopa rasite species, cattle were monitored during a period of six months (O ctober 1992 - March 1993). Four farms were located in the dry pacific region of the canton of Tilaran and a fifth farm on the slopes of the Poas volcano in a cool tropical cloud-forest ecosystem. On each farm 3 to 5 animals of 6 to 24 months of age were selected at random. All ti cks were removed on a monthly basis from the right half side of each a nimal, while the site of attachment was recorded. Ticks were counted a nd differentiated according to species, developmental stage and sex. M oreover, engorged female ticks were assayed for the presence of Babesi a bigemina, Babesia bovis and Anaplasma marginale using the polymerase chain reaction (PCR) multiplex system. Two species of ticks, Amblyomm a cajennense and Boophilus microplus, were encountered on the cattle i n the Tilaran region and one species, B. microplus, was detected in th e Poas region. Two to ten times as many ticks were encountered in the Tilaran region than in the Poas region, which is in accordance with a stable enzootic protozoan disease situation in the former region and a n unstable epizootic situation in the latter region. Nymphal and adult stages of both tick species were present in largest numbers on the ve ntral parts of the animals. PCR analysis of entire ticks indicated ver y high infection rates with hemoparasites of veterinary importance. Th is was in accordance with high seroprevalence rates in the hosts.