Biology of the non-parasitic phase of the cattle tick Rhipicephalus (Boophilus) microplus in an area of Amazon influence.

BACKGROUND: Rhipicephalus (Boophilus) microplus is the most important tick species affecting cattle in the world. Under field conditions, the non-parasitic phase of R. (B.) microplus is unknown in the Amazon biome, including Brazil. The present study aimed to evaluate the non-parasitic phase of R. (B.) microplus in field (grass plots) and laboratory conditions. METHODS: The study was conducted from September 2020 to April 2022 in an Amazonian region (Maranhão State, Brazil). We evaluated the biological parameters of R. (B.) microplus under laboratory and field conditions. Engorged females were exposed to experimental conditions every 14 days, totaling 20 months of study. The following biological parameters were observed: pre-oviposition period, egg mass incubation period, and maximum larval survival period. RESULTS: Abiotic data (e.g., temperature and humidity) varied little throughout the year. Precipitation was the factor that varied the most throughout the year (dry ~ 30 mm3 and rain 400 mm3), and the parameters of pre-oviposition and pre-hatching are longer during the rainy season. A possible negative effect of the dry season on the percentage of hatched eggs was observed. Larval longevity in the plots of both control and free females was short (mean ~ 50-60 days), below that recorded for larvae under controlled conditions (mean ~ 95 days). CONCLUSIONS: Rhipicephalus (Boophilus) microplus was able to complete its non-parasitic phase by producing host-seeking larvae in the pasture during all months of the study. The results indicate that R. (B.) microplus can complete up to six generations per year in biome Amazon. To our knowledge, this is the highest number of annual generations for R. (B.) microplus in Latin America.

Evaluation of a combination of Citrus aurantium var. Dulcis essential oil and albendazole for the treatment of sheep gastrointestinal nematodes.

Citrus fruits are consumed all over the world and their by-products are used for animal feed and essential oils production. This study aimed to evaluate the in vitro and in vivo activity of Citrus aurantium var. Dulcis essential oil (CaEO) combined with ABZ against benzimidazole resistant Haemonchus contortus. In vitro egg hatching assays (EHA) were performed using CaEO and ABZ to estimate the effective concentration to achieve 50% egg death (EC50) values and calculate the test essential oil and drug combinations using a simplex-centroid mixture design. These concentrations were used for a second round of EHAs. Sixteen sheep were randomly allocated into two groups and treated with ABZ and the combination of CaEO and ABZ, and faecal egg count reduction tests were performed. In the first round of EHA, CaEO and ABZ showed EC50 values of 0.57 and 0.0048 mg mL-1, respectively. The H. contortus strain used in the study was shown to be highly benzimidazole resistant, with only 1.5% of parasites having susceptible ß-tubulin SNP genotypes. The ABZ reduced the shedding of nematode eggs by 78%, however, its combination with CaEO reduced faecal egg counts by only 9%. The present study is important to highlight the interferences of natural products in anthelmintic metabolism and consequently in drug efficacy.

Nemabiome metabarcoding reveals differences between gastrointestinal nematode species infecting co-grazed sheep and goats.

Our current understanding of differences in the epidemiology of gastrointestinal nematode (GIN) species in co-grazed sheep and goats is inadequate with reference to the development of sustainable control strategies. The next-generation metabarcoding sequencing method referred to as the 'nemabiome' allows some of these differences to be explored to describe the intensity of co-infecting GIN species. We applied this platform to study sheep and goats that were co-grazed on Guinea grass pasture in northeastern Brazil. Co-grazed goats and sheep were treated with a monepantel anthelmintic, then exposed to the same gastrointestinal nematode species. Overall, there were differences in the prevalence of GIN species identified in the sheep and goats; Trichostrongylus colubriformis and Teladorsagia circumcincta predominated in goat kids, while Haemonchus contortus predominated in adult does, ewes and lambs once burdens became re-established after anthelmintic treatment. Description of the pattern of re-infection following anthelmintic treatment was prevented by the unpredicted poor efficacy of 2.5 mg/kg and 5 mg/kg, respectively, of monepantel against O. columbianum and T. circumcincta in lambs, and T. circumcincta adult does. Differences in drug efficacy between host age and species groups may be important when considering sustainable GIN control strategies for co-grazed animals. The aggregated FECs of the adult does and goat kids representing re-established GIN burdens, were higher than those of the co-grazed adult ewes and lambs. This implies that there are inherent differences in GIN species adaptation to the two naïve small ruminant host species, and shows the need for better understanding of the factors giving rise to this situation associated with exposure to infective larvae and host responses. At the start of the study, the adult does were co-infected with several GIN species, with the highest intensity of T. circumcincta, contrasting with the situation in the adult ewes, in which H. contortus predominated. However, once burdens became re-established after treatment, H. contortus predominated in both adult does and ewes. This demonstrates the potential for host burdens of H. contortus to establish and predominate after anthelmintic treatment when burdens of co-infecting GIN species are low.

In vitro and in vivo activity of hydrolyzed Saccharomyces cerevisiae against goat nematodes.

Haemonchus contortus is the most prevalent nematode in tropical and subtropical regions and is responsible for significant losses in small ruminant production systems. Control of this parasite is based on the use of synthetic anthelmintics; although effective, prolonged and indiscriminate use can select for populations of resistant nematodes. Hydrolyzed yeast can help prevent populations of nematodes and is low in cost. The present study aimed to evaluate the preventive effect of hydrolyzed yeast on H. contortus through in vitro and in vivo assays. In in vitro experiments, the yeast preparation was tested at different stages of the H. contortus life cycle via tests of egg hatchability, larval development, larval exsheathment and larval migration. Both eggs and L3 larvae were obtained from sheep artificially infected with a monospecific strain of H. contortus. In in vivo experiments, animals were treated with hydrolyzed yeast (53.4 mg/kg/BW), and fecal egg counts (FECs), feces culture and Famacha were performed. The yeast preparation inhibited larval exsheathment in a dose-dependent manner (IC95 of 0.46 mg/mL), though no activity at the other stages of the H. contortus life cycle was observed. The hydrolyzed yeast preparation was able to reduce FECs in treated animals from D40 to D54 (p < 0.05), showing an average efficiency of 60%. The yeast exhibited preventive properties, and the IC95 value suggests that H. contortus is highly susceptible. Our results indicate that administration of hydrolyzed yeast, which is already used commercially in ruminant nutrition, is an alternative method for the control of nematodes, mainly H. contortus.

Hemotropic mycoplasmas infection in water buffaloes (Bubalus bubalis) from northeastern Brazil.

Two species of hemotropic mycoplasmas (HM) are known to infect large domestic ruminants, Mycoplasma wenyonii and 'Candidatus Mycoplasma haemobos'. Although HM has been described in cattle worldwide, data in water buffaloes (Bubalus bubalis) remain scarce. Accordingly, the aim was to determine the occurrence of HM in water buffaloes from northeastern Brazil. A total of 101/290 (34.83%) buffaloes were positive for HM (16 M. wenyonii alone, 6 'Ca. M. haemobos' alone and 79 both). This was the first report of M. wenyonii infection in ruminants from Brazil. Clinical signs of hemoplasmosis in buffaloes remain unknown.

[Ectoparasites in goat and sheep folks from Alto Mearim and Grajaú Microregion, State of Maranhão]. / Ectoparasitos em rebanhos de caprinos e ovinos na microrregião do Alto Mearim e Grajaú, Estado do Maranhão.

Goat and sheep folks from Alto Mearim and Grajaú microregion, State of Maranhão, were examined by inspection and by feeling to collected ectoparasites. The specimens were kept in individual bottles for each host sampled with alcohol 70 degrees GL as preserver liquid. The identification was carried out at Universidade Estadual do Maranhão at the laboratory of parasitology. The ticks were examined in stereomicroscope and identified through Aragão and Fonseca (1961) dicotomic key; the lice were mounted in slides according to Pinto (1938) technique, examined in optic microscope and identified through Tuff (1977) and Furmam and Catts (1977) keys; the fly larvae were examined in stereomicroscope and identified by the morphology of the peritreme, and spiracular slits. In 380 animals sampled, 143 (37,64%) were infested with ectoparasites. The following parasites were identified: Bovicola caprae, Boophilus microplus, larvae of Cochliomya hominivorax (screw-worm) and larvae of Dermatobia hominis (bot fly). Parasitary association was observed only in goats in Grajaú and Sítio Novo (louse+tick; louse+bot fly; screw-worm+louse and ticks+louse+screw-worm). The statistic analyses demonstrated that the prevalence of ectoparasites was high in the rainy season (P<0.02).