Biomedical subjects

L M Borges

Publications and source records attributed to L M Borges.

7 recordsLinked to original sources

PubMed2000

Population dynamics of the free-living stages of Amblyomma cajennense (Fabricius, 1787) (Acari: ixodidae) on pastures of Pedro Leopoldo, Minas Gerais State, Brazil.

A study on the population behavior of Amblyomma cajennense larvae, nymphs and adult free-living stages was carried out in Pedro Leopoldo County, Minas Gerais State, Brazil, from July 1995 to July 1997. Larvae were collected from pasture from April to October using the technique of drag sampling with flannelette. The maximal larval population was observed during autumn (May) representing, respectively, 48 and 82% of the total numbers recovered during the first and the second years of the experiment. Nymphs and adults were captured throughout the year by the use of traps with carbon dioxide as chemical attractant. The highest population of nymphs occurred during the winter (July), representing 39.5% of the total collected specimens. Adults had the highest population density on pasture during spring and summer, i.e., from August to May, with peaks in January and February, representing 46 and 38.3% of the total collected specimens during the first and the second year of study, respectively.

Animals↗

PubMed2000

Seasonal dynamics of Anocentor nitens on horses in Brazil.

Anocentor nitens is a widespread ectoparasite of horses in Brazil. A study of the seasonal dynamics of the parasitic phase of this tick was made by regular census of engorging females (>/=4mm) on free-ranging horses, fortnightly from July 1995 to July 1997, at Pedro Leopoldo, Minas Gerais. Twenty horses were divided into four groups of five animals per group, each having a similar mix of resistant and less resistant animals, based on initial infestation. Every 2 weeks, one of the groups, in sequence, was treated with an acaricide to prevent excessive infestations, and female ticks were censused 38 days later. The acaricide dips did not interfere with the seasonal dynamics of the tick population, which produced three major peaks of activity over a 12-month period. The first two peaks were in the hot, wet season and the third in the cold dry season. Tick numbers were similar for the two 12-month periods, decreasing from the spring and summer to the autumn and winter. Infestation rates were not equal among different horses. Twenty percent of the horses were responsible for 48% of the total parasite load, while 30% accounted for only 2.5% of the total parasite load. Principal predilection sites were; the ear (61%), mane (21%), and muzzle and face (6%). Measures for the strategic control of A. nitens ticks are discussed.

Animals↗

PubMed1999

Seasonal dynamics of the free-living phase of Anocentor nitens at Pedro Leopoldo, Minas Gerais, Brazil.

An understanding of seasonal dynamics in the free-living phase of the tropical horse tick, Anocentor nitens, is vital for effective control measures. This study examines seasonal changes in the oviposition and incubation periods, eclosion rates, reproductive success, and larval survival in the free-living phase during the period June 1995-July 1997. Ten engorged female ticks, placed individually in wire-gauze tubes, were exposed in a field of Brachiaria decumbens fortnightly each month, and monitored to measure the duration of the various reproductive parameters, and success. Larval abundance was estimated indirectly, through the percentage of females with viable progeny, and directly by using a flagging method. Duration of the free-living cycle ranged from 12.3 weeks (October and December) to 23.5 weeks (March). The cycle was prolonged in cold and dry months. Larval survival was longer from February to July, and reduced from August to February. Oviposition was recorded in all months, and the egg production index ranged from 26.7 to 47.1%. The eclosion rate ranged from 0.1 to 76.6% in different months. Monthly estimates of larval abundance in the pasture were similar for the two methods used, being higher in months with higher temperatures, relative humidity and rainfall.

Acremonium↗

PubMed1999

Presence of sex pheromones in Anocentor nitens (Acari: Ixodidae).

The aim of this study was to investigate whether there are sex pheromones in the tropical horse tick, Anocentor nitens (Neumann). When virgin males and females, fed on rabbits for 3-7 d, were tested reciprocally, there was a direct correlation between attractiveness and the period of feeding; attraction was greater (and with the fastest responses) in males and females fed for at least 6 d (sexually active males and confirmed attractive females). The capacity of sexually active males to orient topward confirmed attractive females decreased as the emission distance increased; the maximum distance that evoked a response by males was 6 cm. Confirmed attractive females lost their attractiveness approximately 2 h after being separated from the host, or after being killed by ethanol injection, although some females continued to attract sexually active males up to 4 h after death. An extract was produced by immersing confirmed attractive females in hexane and submitting them to ultrasound. Sexually active males were more attracted to and spent more time on glass bead dummies treated with this extract when compared with those treated with the hexane alone. Our results indicate the presence of at least 2 sex pheromones (attractant and mounting) in attractive females of A. nitens.

Animals↗

PubMed1998

Recognition of the tick genus Anocentor Schulze, 1937 (Acari: Ixodidae) by numerical taxonomy.

We report on an evaluation of the systematic position of the tick Anocentor nitens (Neumann), examining particularly whether Anocentor should be regarded as a subgenus of Dermacentor or as a separate genus. Twelve species of Ixodidae were analyzed phenetically by using 24 characters of adult ticks. A phenogram indicated 3 clusters, with Anocentor more closely related to Rhipicephalus than to Dermacentor. The results of this study endorse the validity of the monotypic genus Anocentor.

Animals↗

PubMed1994

Intellectual and developmental differences in external memory strategies.

External memory strategies (e.g., moving objects) were investigated in 11-year-old children with mild mental retardation and 7- and 11-year-olds without mental retardation. Participants attempted to place objects at specified spatial locations after hearing sequences of tape-recorded instructions. During baseline, children with mental retardation and 7-year-olds used external strategies more frequently than did 11-year-olds. All three groups used external strategies after prompting that represented the correct spatial locations, and all used the same tactics. In contrast to expected deficiencies in the use of strategies, results show areas of overlap in strategy capabilities among the groups.

Child↗

PubMedDate not supplied

Host specificity of Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae) with comments on the drop-off rhythm.

The parasitic specificity of larval, nymph and adult Amblyomma cajennense on six different host species: Oryctolagus cuniculus, Rattus norvegicus, Gallus gallus domesticus, Anas platyrhynchus, Coturnix coturnix and Streptopelia decorata is described. In terms of the numbers of larvae and nymphs recovered, O. cuniculus was the best host species. The modal day for drop-off of larvae and nymphs was day three for the mammal hosts, but variable in the birds. We conclude that adult A. cajennense have a strong degree of specificity due to the fact that the tick failed to complete its life cycle on any of the evaluated hosts. The immature stages, on the other hand, showed a low level of specificity, most especially in the larval stage, indicating the existence of secondary hosts which probably serve as dispersers in the wild. The results also indicated a variable drop-off rhythm for larvae and nymphs in two periods, diurnal (6-18 hr) and nocturnal (18-6 hr), which differed depending upon the host.

Adult↗