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In four provinces of north-western Argentina (Catamarca, Jujuy, Salta and Tucumán), between March 1976 and March 1990, 514 ticks were found on humans. They were identified as Rhipicephalus sanguineus group (1 male), Boophilus microplus (6 male, 1 female), Amblyomma parvum (9 male, 13 female), A. cajannense (35 male, 30 female, 81 nymphs), A. neumanni (33 male, 41 female, 144 nymphs) and Amblyomma spp. (10 nymphs, 110 larvae). Most of the ticks were from the phytogeographical region of Chaco, one (B. microplus) was from an ecotone between the Chaco and the Andean Patagonia region, and the remainder of the ticks were from the Amazon region.

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The landscape ecology of Lyme disease was studied in 1989 on 67 residences in an endemic area of Armonk, Westchester County, a northern suburb of New York City. Four main habitat types were defined, and each property was surveyed for immature and adult lxodes dammini ticks; 98.6% of 1,790 ticks collected were I. dammini. Overall, 67.3% were collected from woods, 21.6% from ecotone (unmaintained edge), 9.1% from ornamental vegetation, and 2% from lawns. Larval ticks were concentrated in woods, but nymphs and adults were widely dispersed in all habitats. Tick abundance was positively correlated with property size. Larger properties (greater than or equal to 0.5 acre) were more likely to have woodlots and, hence, more ticks. Dark-field and direct fluorescent microscopic examination of tick midgut tissues revealed that 29.6% of nymphs and 49.7% of adults were infected with Borrelia burgdorferi. Infected nymphs and adults were found on 36% and 60% of properties, respectively. These data indicate that the abundance of ticks capable of transmitting Lyme disease spirochetes is related to landscape features of the suburban residential environment.

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Eight species of ectoparasites were recovered from 35 Sylvilagus audubonii and 35 Lepus californicus occurring sympatrically near the Clovis-Portales area of eastern New Mexico. Recovered were Anoplura (Haemodipsus setoni), Diptera (Cuterebra lepusculi and Cuterebra ruficrus), Siphonaptera (Echidnophaga gallinacea and Euhoplopsyllus glacialis), and Acari (Ornithodoros parkeri, Dermacentor parumapertus, and Haemaphysalis leporispalustris). Jaccard's index showed a 50% ectoparasitic overlap with H. setoni, E. glacialis, D. parumapertus, and H. leporispalustris present on both host species. Cuterebra lepusculi, E. gallinacea, and Ornithodoros parkeri were taken only from S. audubonii, whereas C. ruficrus occurred only on jack rabbits. Euhoplopsyllus glacialis was the only species to demonstrate a preference for sex of host, occurring more abundantly on females.

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Systemic efficacy of ivermectin applied topically was evaluated against the cattle tick, Boophilus microplus. Twenty cattle with induced infestations were randomly allocated to five groups of equal size based on the numbers of engorged female ticks which fell through the slatted floor of individual pens during the 3 days prior to treatments. Control cattle were non-medicated. Cattle in three groups were given ivermectin at 200, 500 or 1000 mcg kg-1 in a topical formulation applied along the backline from the withers to the rump; cattle in the fifth group were given ivermectin in an injectable formulation subcutaneously at 200 mcg kg-1. Individual 24-h tick collections were made three times weekly for 5 weeks after treatment. Engorged female B. microplus were incubated to determine effects on reproduction. Based on the numbers of engorged female B. microplus collected following treatments, overall efficacy of ivermectin applied topically at 200, 500 and 1000 mcg kg-1 was 50, 85 and 91%, respectively, whereas ivermectin given at 200 mcg kg-1 subcutaneously was 80% effective. The index of reproduction for ivermectin given topically was reduced by 84, 94 and 95%, respectively, and that for ivermectin subcutaneously was 94%. No significant differences (P greater than 0.05) were found for these variables between ivermectin given topically at 500 or 1000 mcg kg-1 versus 200 mcg kg-1 given subcutaneously.

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Eighty-two equine sera from 13 farms in northern Colombia were examined for antibodies to Babesia caballi and B. equi using the complement fixation (CF) and the indirect fluorescent antibody (IFA) test. Seroreactors to both piroplasms were present on all farms. The IFA test indicated a prevalence of 90% for B. caballi and 94% for B. equi. The CF test detected antibodies to B. caballi in 41% and to B. equi in 65% of the animals. The prevalence of seroreactors in different age groups revealed a significant decline in CF antibodies to B. caballi in animals older than three years. IFA titres for both Babesia spp. gradually declined with increasing age of the animals but were still present in most animals of the oldest age group (over nine years old). Anocentor nitens was found on all farms whereas Amblyomma cajennese was found only on two farms located on the coast.

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