Evaluation of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) resistance to different acaricide formulations using samples from Brazilian properties

The Rhipicephalus (Boophilus) microplus tick is responsible for considerable economic losses in Brazil, causing leather damage, weight loss and reduced milk production in cattle and results in the transmission of pathogens. Currently, the main method for controlling this tick is using acaricides, but their indiscriminate use is one of the major causes of resistance dissemination. In this study, the adult immersion test (AIT) was used to evaluate resistance in ticks from 28 properties located in five different states (Mato Grosso do Sul, Mato Grosso, Ceará, São Paulo, e Minas Gerais) and the Distrito Federal (DF) of Brazil. The resistance was found in 47.64% of the repetitions demonstrating an efficacy of less than 90% in various locations throughout the country. The larvae packet test was used to evaluate samples from ten properties in four states (Mato Grosso do Sul, Mato Grosso, Minas Gerais and Espírito Santo). Spray products belonging to the main classes of acaricides, including combination formulations, were used in both types of test. New cases of resistance were found on properties within the states of Ceará, Espírito Santo and Mato Grosso, where such resistance was not previously reported.

Contributions of the hair sheep breed Santa Ines as a maintenance host for Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in Brazil

Background

Hair sheep breeds are a new, cost-effective option for the diversification of livestock in the Midwest region of Brazil. They are grazed extensively with cattle as well as in isolation in small areas. Hair sheep breeds are vulnerable to infestation by parasites such as the cattle tick, Rhipicephalus microplus, which causes various types of damage and can transmit diseases.

Methods

In this study, Santa Inês hair sheep were naturally infested in an area contaminated by infested cattle and then monitored to determine the ability of these animals to maintain the local tick population in the absence of cattle. After engorged tick females of each generation fell off, the animals were placed in another pasture and were returned only after larvae reappeared in the original pasture.

Results

Tick counts were performed every ten days for three generations of sheep, and average infestations per animal of 34, 12 and 4 ticks were observed for each successive generation. These numbers suggest the acquisition of resistance; however, additional studies are needed to ensure resistance is achieved. The average length of the parasitic phase for each generation of ticks was 25 days.

Conclusion

We concluded that this hair sheep breed, even if kept separate from cattle, is able to maintain tick populations for at least three generations, although a gradual decrease in the population levels of R. microplus over three generations was observed. We also detected two positive cases of Anaplasma spp. Therefore, it appears that the Santa Inês hair sheep breed contributes to the circulation of this bacterium among other ruminants.

Mechanisms of pyrethroid resistance in Haematobia irritans (Muscidae) from Mato Grosso do Sul state, Brazil

Horn fly resistance to pyrethroid insecticides occurs throughout Brazil, but knowledge about the involved mechanisms is still in an incipient stage. This survey was aimed to identify the mechanisms of horn fly resistance to cypermethrin in Mato Grosso do Sul state, Brazil. Impregnated filter paper bioassays using cypermethrin, synergized or not with piperonyl butoxide (PBO) and triphenyl phosphate (TPP), were conducted from March 2004 to June 2005 in horn fly populations (n = 33) from all over the state. All populations were highly resistant to cypermethrin, with resistance factors (RF) ranging from 89.4 to 1,020.6. Polymerase chain reaction (PCR) assays to detect the knockdown resistance (kdr) mutation also were performed in 16 samples. The kdr mutation was found in 75% of the tested populations, mostly with relatively low frequencies (<20%), and was absent in some highly resistant populations. Addition of TPP did not significantly reduce the LC50 in any population. However, PBO reduced LC50s above 40-fold in all tested populations, resulting in RFs ≤ 10 in most cases. Horn fly resistance to cypermethrin is widespread in the state, being primarily caused by an enhanced activity of P450 mono-oxygenases and secondarily by reduced target site sensitivity.

New records of Muscidae (Diptera) in Campo Grande, MS, Brazil

Synanthropic flies outstanding beside other flies due their relative abundance close to domestic animals and human population, to which they are able to cause myiasis or transmit pathogenic agents. As they're necrophagous they act as corpse decomposers and are useful in the forensic entomology in the post mortem interval determination. This study aimed to know flies diversity and abundance in Campo Grande, State of Mato Grosso do Sul. Captures were made weekly, utilizing three traps baited with decaying fish meat, from June of 2008 to May of 2009 in a remainder ciliary forest of the Embrapa's Cattle Beef Experimental Farm. The dipterans families that were considered and respectively number of collected specimens were: Calliphoridae (105,334); Muscidae (27,999); Sarcophagidae (21,083); Fanniidae (17,759) and Mesembrinellidae (305), totalizing 172,480 dipterous. To the local known species some Muscidae were increased as follows: Neomuscina atincticosta, Pseudoptilolepis elbida, Polietina orbitalis, Polietina flavithorax, Scutellomusca scutellaris, Graphomya analis and Morellia couriae.

Susceptibility of the horn fly, Haematobia irritans irritans (Diptera: Muscidae), to insecticides in Brazil

Since horn fly populations became established throughout Brazil, complaints regarding control failure have increased around the country. A broad survey to evaluate the susceptibility of horn flies to both organophosphate (OP) and pyrethroid insecticides was conducted from October 2000 to April 2003. Bioassays using filter papers impregnated with cypermethrin, permethrin or diazinon were conducted on 154 horn fly populations in 14 states and 78 municipalities. Resistance to cypermethrin, the active ingredient present in most insecticide products for horn fly control in Brazil, was detected in 98.46% of the populations, with resistance ratios (RR) ranging from 2.5 to 719.9. Resistance to permethrin (RRs < 6.3) was found in 96.67% of the populations, despite its lack of use. In general, pyrethroid resistance was detected in 97.18% of the horn fly populations, with frequencies greater than 87% in all regions of the country. The status of susceptibility of horn fly populations in Brazil to insecticides can be characterized by high susceptibility to OPs and widespread resistance to pyrethroids, potentially compromising the efficacy of pyrethroid products in most cases. Although some partial results have previously been presented, a general picture of horn fly susceptibility in Brazil is presented here for the first time.

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).

[Chrysomya (Diptera: Calliphoridae) relative abundance and species seasonality in the Pantanal, State of Mato Grosso do Sul, Brazil]

Species of the genus Chrysomya Robineau-Desvoidy 1830 (Diptera: Calliphoridae) play an important role in public health due to myiasis and transmission of enteropathogens. This study aimed to estimate the relative abundance and seasonality of the three Chrysomya species (C. albiceps, C. putoria, and C. megacephala) that occur in the Pantanal region. The flies were caught by four Wind Oriented Traps, baited with decayed bovine liver. Traps were kept active all over the study carried out from December 2004 to November 2007 at Nhumirim ranch, located at the Nhecolândia subregion, Southern Pantanal. A total of 159,086 Calliphoridae flies were collected and 31.87% of them belonged to the genus Chrysomya. Among calliphorid dipterans the most abundant species was C. albiceps (30.86%), followed by C. megacephala (0.67%), and C. putoria (0.34%). The three Chrysomya species showed similar seasonal fluctuations with two annual population peaks observed in June-August and October-December.

Fimicolous Histeridae coleoptera in Campo Grande, MS, Brazil

Fecal masses recently excreted and/or almost dry were collected weekly in a pasture of Brachiaria decumbens Stapf, from May 1990 to April 1992. The feces were conditioned in 15-liter opaque plastic buckets, containing lateral and top openings, where flasks were fastened for capturing Histeridae beetles present in these masses. Three thousand two hundred ninety-nine specimens were collected belonging to 11 species in the Genus: Phelister, Hister, Euspilotus, Acritus, and Xerosaprinus. The most frequent, constant, and abundant species were Phelister sp. nr. carinifrons and P. haemorrhous.