Molecular identification and phylogenetic analysis of Metarhabditis blumi (Nematoda: Rhabditida)

Association between Duddingtonia flagrans, dimethylsulfoxide and ivermectin for the control of Rhabditis spp. in cattle

Cattle parasitic otitis caused by the nematode Rhabditis spp. is a serious health problem in Brazil, a situation which is confounded by lack of effective control measures. In vitro studies associating biological and chemical control as an alternative method showed promising results. The objective was to evaluate the combined use of Duddingtonia flagrans (AC001), 10% dimethylsulfoxide (DMSO), and 1.9% ivermectin for the in vivo control of Rhabditis spp., in naturally infected Gyr cattle. For this purpose, 48 animals, whose infection in both ears was diagnosed, were randomly assigned to 6 groups: group 1 (ivermectin 1.9%); group 2 (10% DMSO); group 3 (AC001); group 4 (ivermectin 1.9% + 10% DMSO w/v); group 5 (1.9% ivermectin + AC001 w/v); group 6 (10% DMSO + AC001 v/v). The treatments were performed in a single dose, in the right ears, with the left ears remaining untreated, as a control group. There was a significant reduction (p < 0.01) in the number of nematodes in the treated groups in relation to the control, with the following best efficacies: groups 1 and 2, 47% and 52.9%, respectively, 7 days after treatment; groups 3, 4, and 5, 47.8%, 48.6% and 36.7%, respectively, 14 days post-treatment; group 6, 38.4%, 21 days post-treatment. It was concluded that the combination of chemical compounds and D. flagrans in a single application was effective for the in vivo control of Rhabditis spp. in naturally infected cattle.

Raillietia auris (Mesostigmata: Raillietiidae) in cattle in the state of Mato Grosso do Sul, Brazil

Parasitic otitis in cattle, caused by mites, has been reported from several continents. The present study aimed to determine the distribution, prevalence, intensity, mean intensity, and range of the agent in cattle in the state of Mato Grosso do Sul, Brazil. The samples were designed at random, with an acceptable margin of error of 3% and a confidence interval of 99%. A total of 449 animals were sampled immediately after slaughter from 34 different municipalities in the state using the technique of flushing both ear canals. Only Raillietia auris (Leidy, 1872) were found, with a prevalence of 98.6%, mean intensity of 53.78 mites/animal, and a range of 1-323. Impressively, the prevalence found was identical to another survey carried out 39 years ago in the same region. Details about the parasite intensity in different age categories of the animals are presented. The study demonstrates that the prevalence and intensity of infestation by Raillietia auris are high, and in older cattle are higher than young ones.

Morphological, morphometrical, and molecular characterization of Metarhabditis amsactae (Ali, Pervez, Andrabi, Sharma and Verma, 2011) Sudhaus, 2011 (Rhabditida, Rhabditidae) from India and proposal of Metarhabditis longicaudata as a junior synonym of M. amsactae

A new population of Metarhabditis amsactae from India is morphologically, morphometrically, and molecularly characterized. This material is characterized by having 0.65 to 1.14 mm length, lips rounded, and grouped in pairs, stoma with metastegostoma bearing setose denticles, pharynx with metacorpus slightly swollen and fusiform, nerve ring, and excretory pore located at isthmus level, female reproductive system didelphic-amphidelphic with vulva equatorial, female tail conical-elongate with acute tip, male tail conical with large and robust posterior filiform part, spicules free with hooked manubrium slightly bent ventrad, gubernaculum with narrow corpus, bursa open leptoderan with eight genital papillae and phasmids posterior to the GP8. Molecular studies based on 18S and 28S rDNA genes are provided for the first time for the species. In addition, integrated morphological, morphometrical, and molecular characters are compared with other previous records of the species. According to our analysis, Metarhabditis longicaudata and other material described as different species are proposed as new junior synonyms of M. amsactae.

Rhabditis spp., in the Espírito Santo, State of Brazil and evaluation of biological control

The objectives of this study were to describe occurrences of Rhabditis spp. causing parasitic otitis in dairy cattle of Gir breed in the state of Espírito Santo, southeastern Brazil, and to evaluate the biological control of this nematode using the nematophagous fungi Duddingtonia flagrans (AC001) and Monacrosporium thaumasium (NF34). After nematode detection and collection, three groups were formed: two groups that were treated, respectively, with the fungal isolates; and a control group, without fungus. The treatments were as follows: (a) Petri dishes containing the culture medium 2% water agar (WA) + 250 nematodes + AC001; (b) Petri dishes containing 2% WA + 250 nematodes + NF34; and (c) Petri dishes containing only 2% WA + 250 nematodes. After seven days at 27 °C the treatments with fungi were able to capture and destroy the nematodes, with percentages of 82.0% (AC001) and 39.0% (NF34) in relation to the control group. The results demonstrate the occurrence of Rhabditis spp. after animals physical examination and that there was efficacy of the in vitro predatory activity of both fungal isolates. Thus, these results are important because they can assist in future in vivo control of this nematode in cattle.

Entomopathogenic nematodes in agricultural areas in Brazil

Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) can control pests due to the mutualistic association with bacteria that kill the host by septicemia and make the environment favorable for EPNs development and reproduction. The diversity of EPNs in Brazilian soils requires further study. The identification of EPNs, adapted to environmental and climatic conditions of cultivated areas is important for sustainable pest suppression in integrated management programs in agricultural areas of Brazil. The objective was to identify EPNs isolated from agricultural soils with annual, fruit and forest crops in Brazil. Soil samples were collected and stored in 250 ml glass vials. The nematodes were isolated from these samples with live bait traps ([Galleria mellonella L. (Lepidoptera: Pyralidae) larvae]. Infective juveniles were collected with White traps and identified by DNA barcoding procedures by sequencing the D2/D3 expansion of the 28S rDNA region by PCR. EPNs identified in agricultural areas in Brazil were Heterorhabditis amazonensis, Metarhabditis rainai, Oscheios tipulae and Steinernema rarum. These species should be considered pest biocontrol agents in Brazilian agricultural areas.