Wilson Werner Koller

Suscetibilidade de Rhipicephalus (Boophilus) microplus a carrapaticidas em Mato Grosso do Sul, Brasil

The cattle tick, Rhipicephalus (Boophilus) microplus, is one of the most important ectoparasites of bovines, requiring adoption of control measures mainly in Bos taurus herds and its crossbreeds. Its control has becoming increasingly difficult due to selection of resistant populations by commercial products. This study aimed to know the status of cattle tick resistance to acaricides in the state of Mato Grosso do Sul. From October 2003 to October 2006 acaricide bioassays were conducted on cattle ticks from eleven of the most important livestock regions of the state. Adult immersion tests using regular commercial products according to label recommendations were followed by the evaluation of biological parameters. Twelve acaricide products containing one or more of seven active ingredients, from three chemical classes: amidine (amitraz), synthetic pyrethroid (cypermethrin), and organophosphates (chlorfenvinphos, chlorpyriphos, diazinon, dichlorvos, and ethion) were tested. Low tick susceptibility was observed in all ranches, with several populations showing virtually no susceptibility to one or more products. Despite the great variation of susceptibility shown by the populations to each acaricide, a gradient of efficacy of these products was observed. Regardless of the acaricide class, the average efficacy of products containing a single active ingredient (19.94%-64.27%) was generally lower than that showed by the mixtures, pyrethroid-organophosphate (46.38%-82.68%) and between organophosphates (85.28%-97.68%). The mixture containing pyrethroid + OF + synergist + repellent (cypermethrin + chlorpyrifos + citronellal + piperonyl butoxide) showed 100% efficacy, although it was tested in a smaller number of populations. Although comparisons with a susceptible strain have not been made, the low efficacy showed by the several different products tested, strongly suggests that tick resistance is widespread in the state. For this reason, it is recommended the routine peruse of susceptibility tests before selection and use of acaricide products for tick control.

Sazonalidade de Haematobia irritans no Brasil Central

A mosca-dos-chifres (Haematobia irritans) e um dos principais ectoparasitos de bovinos no Brasil. Estudos epidemiologicos sao exigidos devido as dificuldades crescentes do seu controle quimico. Por isso, para um melhor conhecimento da dinâmica populacional sazonal desta mosca foram realizadas contagens a cada 14 dias sobre bovinos para corte, entre 7 e 30 meses de idade, durante o periodo de inverno de 1996 ate o verao de 2002. Foi verificada elevacao nos niveis populacionais de H. irritans (P<0,05), entre as estacoes de cada periodo de infestacao (primavera ate o outono), especialmente na primavera e verao e, as vezes, no outono, seguida de uma queda significativa (P<0,05) no inverno, quando a umidade relativa alcancou niveis inferiores a 60%. Houve uma relacao direta e imediata na contagem de moscas com a variacao da umidade relativa (P<0,05) enquanto que os efeitos mais evidentes da temperatura e a precipitacao pluvio-metrica estiveram associados com contagens feitas 42 a 56 dias depois da leitura desses dados climaticos (P<0,05). As cargas parasitarias mais elevadas (numero medio de moscas por animal) por grupo genetico estudado foram: Aberdeen Angus x Nelore = 173,5 (134-254); ½ Pardo Suico x Nelore = 183,5 (32-540); ¾ Aberdeen Angus x Nelore = 133,0 (18-374) e, Valdostana x Nelore = 219,0 (58-620). A ocorrencia de chuvas torrenciais durante a metade inicial do periodo de infestacao (primavera ate meados do verao), comum na regiao deste estudo, foi considerada a principal responsavel pelos niveis populacionais variando de moderados a baixos verificados nesta epoca em comparacao aqueles verificados no restante do periodo.

Besouros coprófagos (Coleoptera: Scarabaeidae) coletados em Aquidauana, MS, Brasil

Coprophagous beetles were collected from a pasture area using pitfall traps baited with cattle fresh manure, from February to December, 1995. Twenty three species were collected, comprising the following genera: Digitonthophagus, Onthophagus, Dichotomius, Ontherus, Canthon, Canthidium, Ataenius, Aphodius, Pedaridium, Ateuchus, Trichillum, Coprophanaeus, and Megathopomina. Among the species collected Digitonthophagus gazella (Onthophagus gazella) was the most numerous, followed in decreasing order by Ontherus appendiculatus, Trichillum externepunctatum, and Dichotomius anaglypticus. The dung beetles with greater biomass were: D. gazella (Fabr.), O. appendiculatus (Mannerheim), D. anaglypticus (Mannerheim) e D. nisus (Germar). Most of the specimens were collected in the warmer and moister months in the year (February, March, April and December). During drier months, June to October, less than 20% of the total specimens were collected. Among the species, those with greater biomass were collected in the crepuscular-nocturnal period.

Insecticide susceptibility of horn flies, Haematobia irritans (Diptera: Muscidae), in the State of Mato Grosso do Sul, Brazil

Horn fly susceptibility to insecticides was evaluated in the state of Mato Grosso do Sul, Brazil, from October 2000 to September 2002. Insecticide bioassays (n=57) were conducted in 38 ranches from 14 municipalities throughout the state. Horn flies from wild populations were collected on cattle and exposed to filter papers impregnated with cypermethrin, permethrin, or diazinon and mortality was assessed after two hours. Resistance to cypermethrin was detected in all populations, with resistance ratios (RR) ranging from 27.6 to 91.3-fold. Permethrin bioassays provided apparently low levels of resistance (RR<5), however, resistant flies were found in 96.9% of the populations based on diagnostic concentrations. From both pyrethroid bioassays, resistance was detected in 97.4% of the populations. On the other hand, a high susceptibility to diazinon (RR< or =1.1) was detected in all populations. Pyrethroid products, most cypermethrin (92.3%) and deltamethrin (66.7%), were used in all ranches controlling horn flies (97.5%). Insecticide treatments, usually incorrectly applied, were routinely delivered by manual backpack sprayers in most ranches (84.5%). This profile of insecticide use helps to explain the widespread resistance of horn flies to pyrethroids in the state as well as their high susceptibility to the organophosphate. Inadequate control practices contribute to aggravate the resistance problem and its consequences.

Besouros coprófagos (Coleoptera: Scarabaeidae) coletados em Campo Grande, MS, Brasil

Semi-fresh to almost dried cattle dung pats were collected weekly in a pasture of Brachiaria decumbens Stapf, from May of 1990 to April of 1992. The faeces were placed into opaque plastic buckets (15 l) with oppenings at the sides and on the top, occluded with flasks to capture adult coprophagous beetles present in the pats. A total of 18.844 Scarabaeidae specimens were collected, belonging to 37 species of the Genera: Ataenius, Aphodius. Agamopus, Pedaridium, Trichillum, Eurysternus, Dichotomius, Ontherus, Ateuchus, Sulcophanaeus, Gromphas, Digitonthophagus, Onthophagus, and Canthon. Approximately 57% of the species were endocoprids, 35% were paracoprids, and 8% were telecoprids. The most frequent, constant, and abundant species were; Onthophagus hirculus (Mannerheim), Aphodius nigrita (Fabr.), and Ataenius sp.1 (Harold).

Efeito de carrapaticidas/inseticidas "pour-on" sobre adultos do besouro coprófago africano Onthophagus gazella Fabr. (Coleoptera:Scarabaeidae)

In 1989, the dung-beetle Onthophagus gazella Fabr. was imported from the United States to be part of the integrated control program of helminths and horn-fly, Haematobia irritans L. Because there is no information about the effects of pyrethroids on the African beetle survival, the effect of four commercial pour-on insecticides for horn-fly control, on dung-beetle survival was investigated. Fifteen 24 months old, Nelore steers, were randomly assigned to five groups, with three animals/group. Animals in group 1 (control) received no treatment. Groups 2, 3, 4 and 5 were treated on day 0 with Alphamethrin, Cyalothrin, Deltamethrin and Flumethrin, respectively. Individual samples of fecal material (approximately 100 g) were collected from the rectum, on days 1, 4, 8, 11, 15 and 18 after treatment and placed in 500 ml glass vials. Ten live beetles were added in each vial and the survival rate was determined. Beetle mortality was high (P 0,01) in mortality rate among treated groups.

Efeito da mosca-dos-chifres, Haematobia irritans (L.) (Diptera: Muscidae),no ganho de peso de bovinos Nelore

This investigation was carried out due the lack of information about the possible effects of the blood-feeding horn fly, Haematobia irritans (L.), on Nellore cattle. Data were recorded during four rainy seasons (October to April) from 1991 to 1995. In each year, 80 animals were utilized according to the following treatments: twenty-eight 1-year old bulls divided into four groups; twenty 2-year old cattle divided into four groups and thirty-two 3-year old cattle divided into eight groups. Treatments against H. irritans were conduced at about 28-day intervals on half part of each age groups and the remainders groups maintained without treatment as control. The flies were counted at 14-day intervals and the animals weight registered at each 28-day intervals. The values for the mean flies number on the animals of the control groups in the first, second, third and fourth years of this study were: five, five, four and five, in the 1-year old group; 15, 11, 13 and 27, in the 2-year old group, and 55, 31, 40 and 51, in that 3-year old group, respectively. It was observed that higher number of flies (P<0.05) attack adult animals than younger ones. Despite of the low number of flies per cattle, there was a significant weight gain (P<0.05) in favour of treated groups than the controls, which gained 8.6, 16.0 and 10.4% over the period, for groups one, two and three years old, respectively. The weight gain per year was 9, 5, 7 and 8 kg for the 1-year old groups; 26, 10, 23 kg and 12 in 2-year old groups, and 16, 8, 9 and 11 kg in 3-year old groups.

Susceptibility to diazinon in populations of the horn fly, Haematobia irritans (Diptera: Muscidae), in Central Brazil.

From October 2000 to April 2001, insecticide bioassays were conducted in 18 ranches from 10 counties in the states of Mato Grosso and Mato Grosso do Sul, in Central Brazil. Horn flies from wild populations were exposed to diazinon-impregnated filter papers immediately after collection on cattle, and mortality was recorded after 2 h. A high susceptibility to diazinon was observed in all tested populations. The LC50s ranged from 0.15 to 0.64 micro g/cm2, and resistance ratios were always lower than one (ranging 0.1-0.6). Pyrethroid products, most applied by backpack sprayers, have been used since the horn fly entered the region, about 10 years ago. The high susceptibility observed to diazinon indicates that this insecticide (as probably other organophosphate insecticides) represents an useful tool for horn fly control and resistance management, particularly in pyrethroid-resistant populations.

Surtos por Stomoxys calcitrans em gado de corte no Mato Grosso do Sul

The expansion of the alcohol industry has led to the installation of ethanol plants in areas traditionally occupied by beef cattle in the Brazilian Midwest. Stable fly (Stomoxys calcitrans) outbreaks associated with alcohol plants have been reported in Nelore cattle in Mato Grosso do Sul, Brazil, in the last two years. Visits to livestock ranches and alcohol plants were held in mid-November 2009 at the end of S. calcitrans outbreaks in the counties of Angelica and Ponta Pora, MS. Interviews, surveys and collections of immature stages of flies were conducted at the sites and the entomological material was taken to the laboratory for further emergency. High stable fly infestations and cattle bunching behavior were observed during visits. Stable fly breeding sites were found and emergence of adult flies occurred from material collected from both cattle ranches and alcohol plants. The set of information, onsite observation, and sampling results made possible a preliminary epidemiological approach on the dynamics of S. calcitrans outbreaks as well as a discussion of potential risk factors.

Abundance and seasonality of Cochliomyia macellaria (Diptera: Calliphoridae) in Southern Pantanal, Brazil

Cochliomyia macellaria (Diptera: Calliphoridae), known as the secondary screwworm, occurs in the Americas and has medical-veterinary and forensic importance. This study aimed to describe the seasonal fluctuation of this species in the Pantanal region, Central-Western Brazil. From December 2004 to November 2007 fly catches using four windoriented traps baited with decaying bovine liver were carried out at the Nhumirim ranch, Nhecolândia subregion, Southern Pantanal. Traps remained active throughout the study period and collections were carried out on a weekly basis. A total of 159,397 Calliphoridae were caught and C. macellaria (57.33%) was the most abundant species. C. macellaria occurred all over the year showing a bimodal behavior with peaks in May-July (late autumn/early winter) and October-December (spring).