Fábio S. Barbieri

Evaluation of the Efficacy of Acaricides Used to Control the Cattle Tick, Rhipicephalus microplus, in Dairy Herds Raised in the Brazilian Southwestern Amazon.

The adult immersion test (AIT) was used to evaluate the efficacy of acaricide molecules used for control of Rhipicephalus microplus on 106 populations collected in five municipalities in the state of Rondônia in the Brazilian South Occidental Amazon region. The analysis of the data showed that the acaricide formulations had different efficacies on the tick populations surveyed. The synthetic pyrethroids (SPs) acaricides were the least effective (48.35–76.84%), followed by SP + organophosphate (OP) associations (68.91–81.47%) and amidine (51.35–100%). For the macrocyclic lactones (MLs), the milbemycin (94.84–100%) was the most effective, followed by spinosad (93.21–100%) and the avermectins (81.34–100%). The phenylpyrazole (PZ) group had similar efficacy (99.90%) to the MLs. Therefore, SP acaricides, including associations with OP, and formulations based on amidine presented low in vitro efficacy to control the R. microplus populations surveyed.

Description of the larva of Amblyomma ovale Koch, 1844 (Acari: Ixodidae) by light and scanning electron microscopy

Abstract The larval stage of Amblyomma ovale Koch is described using optical and scanning electron microscopy. Unfed larvae were obtained from a colony of A. ovale originating from engorged females collected on domestic dogs from Monte Negro County, state of Rondônia, Western Amazon, Brazil. Fifteen larvae were prepared and mounted on slides, and observed under a light microscope equipped with a drawing tube. Five specimens were prepared for scanning electron microscopy. Several morphological characters are described for the first time, including the chaetotaxy of the idiosoma, palps and Hallers organ, as well as morphological features of the idiosoma, gnathosoma and legs. In addition, topographical and numerical patterns of integumentary pores (porotaxy) on the idiosoma of larval A. ovale are described using a recently proposed nomenclature. Three types of integumentary pores were identified on the idiosoma of A. ovale larvae: lyrifissures, small glands, and large wax glands. These structures were observed isolated or associated over the entire idiosoma, except on the scutum, which lacks large wax glands. Larvae of A. ovale showed similar topographical and numerical patterns of integumentary structures, with 6 pairs of large wax glands (1 pair dorsal/5 pairs ventral), 24 pairs of lyrifissures (11 pairs dorsal/13 pairs ventral), and 54 pairs of small glands (32 pairs dorsal/22 pairs ventral). These topographical and numerical patterns of integumentary structures of larval A. ovale showed only minor differences when compared with patterns of other Amblyomma larvae; however, a few key features can be used to differentiate A. ovale from other members of its genus.

Topographical and numerical study of the idiosomal integumentary structures of the larva of four Neotropical species of Amblyomma Koch, 1844 (Acari: Ixodidae).

Integumentary structures of the larvae of Amblyomma longirostre (Koch, 1844), A. parvum Aragão, 1908, A. rotundatum Koch, 1844 and from three populations of A. cajennense (Fabricius, 1787) were studied using light microscopy. A new nomenclature for the localisation of the integumentary structures is proposed. Three types of integumentary structures were identified in the larval idiosoma of the four Amblyomma species: lyrifissures, small glands and large wax glands. These structures were observed isolated or associated over the entire idiosoma, except in the scutum, which lacked lyrifisures and large wax glands. Large wax glands were the most stable within and between the tick species, followed by lyrifissures and small glands. Small glands, although relatively stable, showed the highest number of numerical variations within and between the tick species. Even though there were intra-population variations in the topographical and numerical pattern of some integumentary structures of A. cajennense larvae, there was a definitive pattern for most of the specimens, as showed by the similar modal and mean numbers of integumentary structures per tick side. The patterns of lyrifissures, small glands and large wax glands showed little differences when compared between the four Amblyomma species; however, a few differences were well evident. These differences were sufficient to differentiate larvae of the four species. Thus, we expect that the study of integumentary structures on the larvae of other Amblyomma species will be useful in future taxonomic keys for the identification of Amblyomma larvae from the Neotropical region.

Description of larva of Amblyomma romitii (Acari: Ixodidae) by optical and scanning electron microscopy, including porotaxy and phylogenetic analysis

The description of the larva of Amblyomma romitii Tonelli-Rondelli is based on optical and scanning electron microscopy. Larvae were obtained under laboratory conditions from an engorged female collected on capybara from Rurópolis municipality, State of Pará, Northern Brazil. Several characters are presented including the chaetotaxy of idiosoma, palpi and Haller’s organ. The larval porotaxy (topographical and numerical patterns of integumentary structures) was presented and compared to that of the other Amblyomma spp. larvae. The mitochondrial 16S rDNA partial sequence of A. romitii generated in the present study was aligned with sequences previously determined for other Amblyomma species available in Genbank and with some species presently sequenced. The larval morphology of A. romitii and other Neotropical Amblyomma spp. larvae is discussed as well as the DNA sequence and its phylogenetic position among other species of the genus.

Description of the larva of Amblyomma pacae Aragao, 1911 (Acari: Ixodidae) by light and scanning electron microscopy

Abstract The larval stage of Amblyomma pacae Aragão is described using optical and scanning electron microscopy. Unfed larvae were obtained from a colony of A. pacae originating from engorged females collected on Agouti paca (Linnaeus) from Monte Negro County, state of Rondônia, Western Amazon, Brazil. Several morphological characters are described for the first time, including the chaetotaxy of the idiosoma, palpi and Hallers organ, as well as morphological features of the idiosoma, gnathosoma and legs. The topographical and numerical patterns of integumentary pores (porotaxy) of the larva are described using a recently proposed nomenclature. Only a few morphological differences were observed between the A. pacae larva and other Amblyomma spp. larvae previously described from Brazil; however, some of these characters can be used to differentiate A. pacae from other species of this genus.

Figure 2. Amblyomma Oblongoguttatum Larva. Tarsus I In Redescription Of The Larva Of Amblyomma Oblongoguttatum Koch, 1844 (Acari: Ixodidae) By Light And Scanning Electron Microscopy

FIGURE 5 – 10. Amblyomma oblongoguttatum larva. 5. Gnathosoma, dorsal view (30 µm); 6 Gnathosoma, ventral view (30 µm); 7. Detail of tibiotarsus and hypostome (30 µm); 8. Detail of scutum (30 µm); 9. Coxae I – III (20 µm); 10. Tarsus I, dorsal view (30 µm).