Risk of babesiosis and anaplasmosis in different ecological zones of Santa Cruz Department, Bolivia.

A cross-sectional study was done of seroprevalence of Babesia bigemina, B.bovis, and Anaplasma marginale in cattle from eastern Bolivia, to characterise the risk of tick-borne disease in three ecological zones. Nineteen farms were sampled in the subtropical humid zone, 13 in the dry subtropical zone and nine in the lower western valleys of the Andean massif. The enzyme-linked immunosorbent assay was used. All three pathogens were widespread. For B. bovis, seroprevalences were high (75-78%) in the two subtropical zones which thus had low risk of disease from this infection; but the western valleys were endemically unstable with higher risk. For B. bigemina, seroprevalences were lower (24-57%) in the two subtropical zones and thus these areas were endemically unstable for disease from this infection. However, the seroprevalence of B. bigemina in the western valleys was too low (13%) for risk of disease in susceptible cattle to be considered high. For A. marginale, the seroprevalences in the two subtropical zones were low (19-32%) and very low (6%) in the western valleys suggesting all these zones were endemically unstable for anaplasmosis. Data for individual farms were analysed for risk of both forms of babesiosis; this showed low risk of disease in the subtropical humid zone, higher risk in the dry subtropical zone and variable risk in the western valleys.

Formulation of integrated control of Boophilus microplus in Paraguay: analysis of natural infestations.

A 3-year study into the seasonal variation in the numbers of Boophilus microplus ticks infesting three breeds of beef cattle in Paraguay was carried out to provide the basic data necessary to formulate tick control recommendations. The effect of tick burden on weight gain was also analysed. Economic parameters for tick control were calculated. Half body counts of standard female B. microplus were carried out every 2 weeks, at the same time engorged female ticks were placed in the field to observe time to oviposition, larval hatching and 50% survival time. Cattle were weighed every 2 months. Peak tick burdens were encountered in late autumn, with a winter low. Observations of the non-parasitic cycle of the tick suggested that four generations year-1 were possible. High tick burdens were well correlated to low weight gains or weight losses, depending on the breed of cattle. Compensatory weight gains were seen in all three breeds at the end of winter when tick burdens decreased. The economic threshold for tick treatment was calculated at 53 and 54 ticks per animal in 2 separate years of the study. Recommendations for tick control programmes are given.

Amblyomma variegatum ticks and the occurrence of bovine streptothricosis in Antigua.

The association between the occurrence of Amblyomma variegatum ticks and streptothricosis was studied on the Caribbean island of Antigua. The prevalence of streptothricosis was higher on animals having A. variegatum ticks compared to that of animals not infested with A. variegatum ticks. There was a steady increase in the prevalence of severe lesions as the level of infestation with adult A. variegatum ticks increased. However the distribution of skin lesions could not be related to the predilection feeding sites of adult A. variegatum ticks.

Amblyomma variegatum ticks and the occurrence of bovine streptothricosis in Antigua

The association between the occurrence of Amblyomma variegatum ticks and streptothricosis was higher on animals having A. variegatum ticks compared to that of animals not infested with A. variegatum ticks. There was a steady increase in the prevalence of severe lesions as the level of infestation with adult A. variegatum ticks increased. However the distribution of skin lesions could not be related to the predilection feeding sites of adult A. variegatum ticks (Summary)

The health handicap of schistosomiasis to children in Southern Africa.

To find out more about the health handicap caused by schistosomiasis the most meaningful approach lies in comparing populations with and without the infection. Several studies on appropriately matched groups of South African Black children have failed to reveal clear-cut disadvantages in the infected. Limited studies on White children have shown impairment in the infected. Among Black adults, the very few studies made have shown reduction of working capacity to be slight. Obviously, further comparative studies are required, more particularly on adults. Knowledge of the precise public health burden of schistosomiasis remains unsatisfactory, and a large amount of further research is required to secure the requisite information on morbidity and mortality.