Quantitative Monitoring of Selected Groups of Parasites in Domestic Ruminants: A Comparative Review

Gastrointestinal parasitic worm burdens and efficacy of deworming practices in growing beef cattle grazing California pastures

Treatment for enteric parasites is a common practice in beef cattle, yet little data is known about the prevalence of nematode and trematode parasite infections in beef cattle in the western United States. Likewise, the data on the efficacy of deworming practices and the presence of anthelmintic resistance (AR) of these parasites in this region is sparse. The current study collected evidence for the presence of nematode and trematode parasites in 18 herds of young beef cattle grazing either dryland or irrigated pasture in northern California as well as on efficacy and evidence of AR in a subgroup of herds. We found variable levels of fecal egg counts (FEC) ranging from 6 to 322 for the arithmetic mean eggs per gram (EPG) in the tested cattle groups. There was no difference in the number of EPG between herds grazing dryland or irrigated pasture (P = 0.54). We did not find any evidence for liver flukes or lungworms in the tested cattle. There was evidence of AR to macrocyclic lactones in all eight herds where fecal egg count reduction tests (FECRT) were performed, however due to types and execution of treatment applications and sample sizes, these results need to be interpreted with caution. The most common genus of third stage larvae in coproculture testing before treatment was Cooperia (between 55% and 98% of larvae) as well as post treatment for those herds undergoing FECRT (between 50% and 96%). Ostertagia was the second most frequent genus of larvae found in coproculture testing making up between 0% and 27% of larvae before treatment and between 5% and 50% of larvae after treatment. Anthelmintic practices in beef herds in northern California and likely in a larger geographic area in the western United States need to be updated in order to continue effective use of the currently available drugs.

A Diverse Virome Is Identified in Parasitic Flatworms of Domestic Animals in Xinjiang, China

Parasitic flatworms infect diverse vertebrates and are major threats to animal and even human health; however, little is known about the virome of these lower life forms. Using viral metagenomic sequencing, we characterized the virome of the parasitic flatworms collected from major domestic animals, including Dicrocoelium lanceatum and Taenia hydatigena, Echinococcus granulosus sensu stricto and Echinococcus multilocularis. Seven and three different viruses were discovered from D. lanceatum and T. hydatigena, respectively, and no viral sequences were found in adult tapeworms and protoscoleces of E. granulosus sensu stricto and E. multilocularis. Two out of the five parasitic flatworm species carry viruses, showing a host specificity of these viruses. These viruses belong to the Parvoviridae, Circoviridae, unclassified circular, Rep-encoding single-stranded (CRESS) DNA virus, Rhabdoviridae, Endornaviridae, and unclassified RNA viruses. The presence of multiple highly divergent RNA viruses, especially those that cluster with viruses found in marine animals, implies a deep evolutionary history of parasite-associated viruses. In addition, we found viruses with high identity to common pathogens in dogs, including canine circovirus and canine parvovirus 2. The presence of these viruses in the parasites implies that they may infect parasitic flatworms but does not completely exclude the possibility of contamination from host intestinal contents. Furthermore, we demonstrated that certain viruses, such as CRESS DNA virus may integrate into the genome of their host. Our results expand the knowledge of viral diversity in parasites of important domestic animals, highlighting the need for further investigations of their prevalence among other parasites of key animals. IMPORTANCE Characterizing the virome of parasites is important for unveiling the viral diversity, evolution, and ecology and will help to understand the "Russian doll" pattern among viruses, parasites, and host animals. Our data indicate that diverse viruses are present in specific parasitic flatworms, including viruses that may have an ancient evolutionary history and viruses currently circulating in parasite-infected host animals. These data also raise the question of whether parasitic flatworms acquire and/or carry some viruses that may have transmission potential to animals. In addition, through the study of virus-parasite-host interactions, including the influence of viral infection on the life cycle of the parasite, as well as its fitness and pathogenicity to the host, we could find new strategies to prevent and control parasitic diseases.

Identification of ectoparasitic insects among domestic goats in Bulgaria

Background and Aim

Ectoparasitic entomoses cause serious economic losses to small-scale farmers. Parasites have both direct and indirect impacts on hosts. Domestic goats are a common target of infestation with ectoparasitic insects. This study aimed to identify the species of ectoparasitic insects in domestic goats in Bulgaria.

Materials and Methods

The study was performed in 34 farms from 29 settlements in 16 regions of Bulgaria. A total of 4599 goats from eight breeds, naturally infested with ectoparasitic insects were included in the study. The goats were inspected with a magnifying glass for the presence of skin changes (alopecia, dandruff, crusts, and nodules), eggs and adult ectoparasites. The detected insects were collected individually with tweezers and preserved in containers with 70% ethanol. Over the study period, 5,651 insects were collected; their species, sex, and developmental stage were identified by their morphological features and biometric measurements.

Results

Six species from 5 genera were detected: Linognathus stenopsis Burmeister, 1838; Linognathus africanus Kellog and Paine, 1911; Bovicola caprae Gurlt, 1843; Pulex irritans Linnaeus, 1758; Hippobosca equina Linnaeus, 1758; and Lipoptena cervi Linnaeus, 1758. Linognathus stenopsis were the most prevalent, followed by B. caprae and P. irritans. In detected lice populations, female insects were more numerous; female: male ratios ranged from 2.2 to 7.2 and imagines prevailed over the nymphs. In fleas, male imagines were more numerous than females (1:0.8).

Conclusion

The study demonstrated that the species L. stenopsis, L. africanus, B. caprae, and P. irritans were encountered in more than 40% of surveyed farms, situated in 68.75% of regions in Bulgaria. The most intense infestation was by species from the Linognathus genus (907 insects), whereas the highest extensity of infestation was registered for P. irritans (32.3%). This study detected P. irritans as the only flea species.