Objective--To evaluate the efficacy of coumaphos, an organophosphate (OP) acaricide, at concentrations up to 2 times higher than the highest concentration required by the US Eradication Program against all stages of an OP-resistant strain of Boophilus microplusin experimentally infested cattle. Animals--16 tick-naïve 200-kg female Hereford calves. Procedure--Four groups of cattle (4 calves/group) were all infested with Boophilus ticks 3 times before treatment. Each group was treated with coumaphos as follows: group 1, at 0.165% active ingredient (AI); group 2, at 0.299% AI; group 3, at 0.566% AI; and group 4, not treated. Following treatment, ticks were collected for 21 days. Ticks collected 1 to 7, 8 to 14, and 15 to 21 days after treatment were considered adults, nymphs, and larvae, respectively, at time of treatment. Results--Overall control at 0.165, 0.299, and 0.566% AI was 52.9, 75.8, and 89.7%, respectively. Control of adults ranged from 4.3% at 0.165% AI to 73.5% at 0.566% AI. Control of nymphs ranged from 60.6% at 0.165% AI to 97.3% at 0.566% AI. Control of larvae was > 98% at all coumaphos concentrations. Conclusions and Clinical Relevance--All coumaphos concentrations failed to provide acceptable control for use in the US Eradication Program against OPresistant ticks. Treatment was least effective against adults and most effective against larvae. Even at 0.566% AI (2 times higher than required by the US Eradication Program), ticks were not eradicated, placing the United States at risk from dispersing cattle harboring viable ticks to uninfested areas.

Boophilus microplus, B. annulatus, Hereford heifers (exper.), permethrin or fenvalerate applied as sprays, both pyrethroids could provide adequate reduction in control programs however both acaricides failed to provide the necessary reduction to achieve complete elimination

tick infestations did not cause suppressed immune responses to Anaplasma marginale vaccination in calves, anaplasmosis did not prevent calves from developing resistance to tick reinfestation which was accompanied by immediate hypersensitivity reactions against homologous tick extracts, Dermacentor albipictus did not seem to share common antigenic determinants with Boophilus microplus

Babesia occultans n. sp. originally obtained from engorged female Hyalomma marginatum rufipes collected from cattle in Northern Transvaal, transmission studies in laboratory strain of ticks and splenectomized cattle, morphological, serological, and cross-immunity studies distinguished parasite as previously undescribed species highly infective for H. marginatum rufipes but of low virulence in cattle, unsuccessful attempt to transmit transovarially with Boophilus microplus

Boophilus microplus engorged females stored at 4 C for up to 5 days and females kept at room temperature for 1 day and then at 4 C for 1 day showed no significant differences in their response to an organophosphate (dioxathion) as determined by the Drummond adult test

Amblyomma hebraeum, purification procedure used to obtain pure toxic components of tick eggs, characterization of toxin structure, histopathologic lesions observed in guinea pigs inoculated with egg extract or purified toxin, lesions in guinea pigs inoculated with crude egg extracts of 3 other ticks were histopathologically similar

Relatively little research has been carried out on the behavioral ecology of B. microplus larvae in pasture, this being the principal objective of the current work. Six releases were made in winter (June-August, 1998) and in summer (November-January, 1998/1999). The tick larvae were laboratory reared in 20 adapted plastic syringes. Its were opened and placed in pastures of Brachiaria decumbens, at the research center of the Embrapa Gado de Leite, in Juiz de Fora city, Minas Gerais estate, Brazil. The larvae were observed three times per day, three days per week. The time taken for the larvae to reach the extremities of the grass was mainly related to the air temperature. In summer, the larvae formed smaller and less active aggregations than in winter. This behavior was considered to be a mechanism to avoid overheating and increase ventilation to save energy. Their horizontal and vertical migrations were considered a behavioral strategy to avoid the direct rays of the sun. | Existem relativamente poucos trabalhos sobre ecologia e comportamento das larvas de Boophilus microplus na pastagem, tendo sido este o principal objetivo do presente trabalho. Foram monitoradas seis repetições no inverno de 1998 e seis no verão de 1998/1999. As larvas foram acondicionadas em 20 seringas plásticas adaptadas e disponibilizadas em pasto constituído pela gramínea Brachiaria decumbens, na Embrapa Gado de Leite, em Juiz de Fora, estado de Minas Gerais, permitindo sua dispersão. Foram realizadas três observações diárias, três vezes por semana. Verificou-se que o tempo que as larvas levam para alcançar as extremidades da gramínea é condicionado principalmente pela temperatura. No verão, as larvas formam agrupamentos menores e menos ativos do que no inverno. Este comportamento sugere minimizar o superaquecimento e aumentar a ventilação, economizando energia. As migrações horizontal e vertical ocorrem como estratégia comportamental contra a ação direta dos raios solares.