similis (Nematoda: Trichostrongylidae) in cattle and sheep from shared pastures in São Paulo State, Brazil

The production costs of Haemonchus contortus and other nematode parasites in pre-weaned beef calves in New Zealand

Haemonchus contortus can frequently be found infecting pre-weaned beef calves on sheep and beef farms around the North Island of New Zealand. The purpose of this study was to consider whether the presence of this parasite alone, or as part of a mixed infection, could be impacting growth rates of young animals, on three commercial farms in the North Island of New Zealand. Trials were conducted on commercial sheep and beef farms in each of the Northland, King Country and Gisborne regions, in late summer/autumn (February to April) of 2016 to measure the effect of treatment with narrow and broad spectrum anthelmintics on liveweight gain of spring-born calves pre-weaning. Each farm was chosen based on the presence of Haemonchus and that it was a beef cow/calf system with the cows and calves grazing the same pastures as sheep at some stage. Three sampling visits were made to each farm with the animals being weighed, faecal sampled and treated with one of two anthelmintics (Closantel alone to remove only Haemonchus or a triple combination containing moxidectin, levamisole and oxfendazole to remove all nematodes) or left untreated, on each of the first two visits. There was no significant difference in liveweight gain between any of the treatment groups, hence there was no evidence for an impact of Haemonchus alone, or a mixed nematode infection, on pre-weaned calf growth rates on these farms. It remains unclear whether there may be a justification to consider treatment of calves should they constitute a significant source of pasture larval infestation with H. contortus, in an integrated cattle-sheep system.

Scanning electron microscopy of different vulval structures in a Mexican Haemonchus contortus isolate

Haemonchus contortus is a parasite species that affects the health and production of grazing small ruminants in different parts of the world. Scanning electron microscopy (SEM) is an important tool for the study of parasites' morphology and taxonomy as it generates images that appear 3D and are generally easier to interpret than optical microscopy images. This study used the SEM to describe the vulval types of adult H. contortus from a Mexican isolate. A total of 14 adult H. contortus females were obtained from two artificially infected goats. Females were fixed and processed by critical point drying and observed with SEM. A collection of SEM images was obtained from these parasites and those images were used to identify the structures previously described by optical microscopy studies. Two different types of vulval structures were described in this Mexican H. contortus isolate: Type 1 (vulval flap), Type 2 (epiptygma). An unusual vulval structure was reported in a single individual. The Type 1 included vulval flaps of different sizes and spatial dispositions, as well as one or more knobs in different positions around the vulva. The Type 2 shows differences in the epiptygma. The present study suggests that the Mexican H. contortus isolate used in donor animals possess intraspecific polymorphism in vulval structures.

Is there competition between Haemonchus contortus and Haemonchus placei in a pasture grazed by only sheep?

This study aimed to evaluate the dynamics of Haemonchus contortus and Haemonchus placei infections and hybridization between these species in grazing sheep without contact with cattle. On January 14, 2014, sixteen young sheep were infected with 4000 infective H. placei third-stage larvae L3; 11 days later, another group n = 16 was infected with 4000 H. contortus L3. The establishment rates of H. contortus and H. placei L3 were, on average, 61.6 % and 56.8 %, respectively, in the permanent sheep. After the establishment of patent infections, all permanent sheep were allocated together in the same clean pasture where they grazed for the next 12 months. Euthanasia of a sample of the permanent sheep was performed every three months: in May, August, November and February. Two weeks before the sheep were removed for euthanasia, 2 worm-free tracer sheep were introduced to the pasture to evaluate the larval population in the field. The tracer sheep grazed alongside the permanent sheep for 2 weeks. Then, they were housed indoors for 20 days; at the end of this period, they were euthanized. Parasites were recovered from the permanent and tracer sheep and identified using morphological and molecular techniques. A total of 432 worms (from permanent and tracer animals) were analyzed by PCR using species-specific primer pairs. Of these specimens, only two (0.46 %) male worms were identified as hybrids: one was recovered from a permanent animal euthanized in August and the other from a tracer sheep that grazed in May. The last detection of adult H. placei worms occurred in sheep euthanized in May (approximately 3.5 months after the beginning of the grazing period). The morphological evaluation of the L3 produced in fecal cultures showed that H. placei were progressively replaced by H. contortus populations starting in March. The last trace of H. placei L3 was found in August, when a small percentage (0.5 %) of infective larvae with H. placei morphology was identified in a fecal culture. In conclusion, hybridization between H. contortus and H. placei can occur in the field during coinfection. It was demonstrated that H. placei established successfully in artificially infected worm-free sheep; however, with concomitant natural reinfection with H. contortus, the H. placei population showed a rapid decrease and was eliminated within a few months in an environment without cattle.

Establishment of co-infection and hybridization of Haemonchus contortus and Haemonchus placei in sheep

This study aimed to evaluate the simultaneous infections of Haemonchus contortus and Haemonchus placei in sheep, as well as the production of hybrids. A parental group of lambs (n = 6) were mix-infected with 2000 infective larvae (L3) of H. placei and 2000 L3 of H. contortus. Faecal samples were taken from each of these six lambs to produce the first generation of L3 (F1-L3) in individual cultures. These F1-L3 were used to infect 12 lambs; six of them were euthanized at 42 days (Group F1-42) and six at 84 days (Group F1-84) post infection. Polymerase chain reaction (PCR) analysis, using species-specific primer pairs, was the gold standard method for identification of Haemonchus adult species and hybrids. The establishment rate of both species was similar in the parental group: 51.7% H. contortus and 48.3% H. placei. Of the 219 adult specimens from groups F1-42 and F1-84 analysed by PCR, eight (3.65%) were hybrids, 111 were H. contortus and 100 were H. placei. The morphological evaluation of the F1-L3 from the parental group showed a predominance of larvae with H. contortus size (51.5%) in comparison with H. placei (42.8%). In the second generation of L3 (F2-L3) produced by the F1-lambs, larvae with H. contortus morphology predominated, with 81.5% in the F1-42 group and 84.0% in the F1-84 group. In conclusion, an artificial mixed infection by H. contortus and H. placei was established in lambs and resulted in the production of a small number of hybrids among their offspring.

Helminth infections and hybridization between Haemonchus contortus and Haemonchus placei in sheep from Santana do Livramento, Brazil

The occurrence and intensity of helminth infections were evaluated in sheep from pastures shared with cattle. In 2015 and 2016, young male sheep acquired in Santana do Livramento, Rio Grande do Sul, Brazil, were finished in integrated crop-livestock system. We selected the 12 sheep that showed the highest number of nematode eggs per gram of faeces to search for worms in the gastrointestinal tract. Haemonchus contortus and Trichostrongylus colubriformis were the major parasites. H. contortus presented mean intensities of 1,159 and 257 worms in 2015 and 2016, respectively. T. colubriformis displayed mean intensities of 4,149 and 2,427 worms in 2015 and 2016, respectively. Of the 127 male specimens of Haemonchus spp. analysed by Polymerase Chain Reaction (PCR), 125 were H. contortus, one Haemonchus placei and one hybrid. Other species detected were Cooperia punctata , Cooperia pectinata, Cooperia spatulata, Cooperia curticei, Ostertagia ostertagi, Teladorsagia circumcincta , Trichostrongylus axei, Nematodirus spathiger , and Trichuris ovis. Twenty lambs presented cysts of Taenia hydatigena in the liver and mesentery. One lamb presented Coenurus cerebralis, the larval stage of Taenia multiceps, in the brain. In conclusion, sheep from pasture shared with cattle presented a high diversity of nematode species. H. contortus and H. placei co-infection occur with consequent hybridization.

Effect of the infection with the nematode <i>Haemonchus contortus</i> (Strongylida: Trichostrongylidae) on the haematological, biochemical, clinical and reproductive traits in rams

This study aimed to investigate the effect of Haemonchus contortus infection on rams’ haematological, biochemical and clinical parameters and reproductive performances. A total number of 12 Barbarine rams (control and infected) were included in the experiment. The infected group received 30 000 H. contortus third-stage larvae orally. Each ram’s ejaculate was immediately evaluated for volume, sperm cell concentration and mortality rate. At the end of the experiment (day 82 post-infection), which lasted 89 days, serial blood samples were collected in order to assess plasma testosterone and luteinising hormone (LH) concentrations. There was an effect of time, infection and their interaction on haematological parameters (p < 0.001). In infected rams, haematocrit, red blood cell count and haemoglobin started to decrease from 21 days post-infection. There was an effect of time and infection for albumin. For total protein, only infection had a statistically significant effect. For glucose, only time had a statistically significant effect. Concentrations were significantly lower in infected rams compared to control animals. A significant effect of infection and time on sperm concentrations and sperm mortality was observed. The effect of infection appears in time for sperm concentrations at days 69 and 76 post-infection. Sperm mortality rate was significantly higher in infected animals at day 46 post-infection when compared to control group (p < 0.05). Finally, plasma testosterone traits (average concentration, cumulated levels during the sampling period and pulse frequency) were depressed in infected rams when compared to control counterparts; none of these endocrine traits were affected for plasma LH.

Overview of anthelmintic resistance of gastrointestinal nematodes of small ruminants in Brazil

Abstract Frequent and inappropriate use of all classes of antiparasitic drugs in small ruminants has led to failures in their effectiveness, culminating in a global problem of anthelmintic resistance. Brazil stands out as one of the world’s leaders in publications about anthelmintic resistance, and for having the most numerous reports of this resistance in small ruminants in the Americas. These studies have involved mainly the fecal egg count reduction test (FECRT) and its correlation with field management practices. In vivoeffectiveness testing is conducted in areas where livestock is of greater economic significance, e.g., in the South (sheep) and Northeast (goats), or is important for research and economic centers, such as the Southeast (sheep). The most widely studied species is sheep, for which the widest range of drugs is also evaluated. Despite significant advances achieved in molecular research, laboratory analyses should include knowledge about the reality in the field so that they can become feasible for the producer. Moreover, molecular studies can be underpinned by the analysis of field studies, such as the maintenance of antiparasitic effectiveness over time and the mechanisms involved in this process.