Cooperia oncophora

Cooperia oncophora is one of the most common intestinal parasitic nematodes in cattle in temperate regions. Infections with C. oncophora may result in mild clinical symptoms, but can lead to weight loss and damage of the small intestine, especially when co-infections with other nematodes such as O. ostertagi occur. Infections are usually treated with broad-spectrum anthelmintics such as benzimidazole, but resistance to these drugs has developed in the last decades and is now very common. C. oncophora has a direct life cycle. Infective larvae are ingested by the host. The larvae grow to adults, which reproduce in the small intestines. Eggs are shed onto the pasture with the faeces, which leads to new infections. Co-infections with other gastro-intestinal nematodes such as O. ostertagi and H. contortus are common. C. oncophora females are about 6–8 mm long, males about 5.5–9 mm. They are light red in color and have a coiled shape. Male worms have a large bursa as shown in Figure 2a. The spicules are 240-300 µm long and have a rounded end and a longitudinal line pattern. L3 stage larvae are hard to differentiate between different species, because they are very similar interspecies-wise. Eggs of C. oncophora however can be easily identified by their parallel walls. The life cycle of C. oncophora is direct. Free-living L3 stage larvae residing on the pasture are taken up by grazing cattle and pass to the small intestine. Here, they molt to L4 larvae and then to adults. Eggs are passed in the faeces to the pasture. The larvae hatch and grow to L3 stage larvae. Infective L3 stage larvae are then again taken up by grazing cattle and the life cycle repeats. The pre-patent period, which includes the time between infection and egg laying, lasts between two and three weeks. Like other trichostrongylids, early C. oncophora L4 larvae are able to arrest their development under unfavourable environmental conditions such as low temperatures and high dryness, a process termed hypobiosis. L4 larvae can stay arrested up to five months. Arrested development is characterized by a large number of individuals stopping at the same stage of development, a bimodial distribution of worm sizes, and a recent exposure of the host animal to the infectious agent prior to the prepatent period of the infectious agent. During this period of arrested development, the worms stop growing and slow down their metabolism. Arrested development allows the worms to evade many of the anthilmentics commonly used. The recommended doses are based on adult worms and normally developing larvae. Arrested development can be triggered by the following situations: seasonal influences on the larvae while outside the host, the normal host immune response interrupting the normal parasitic phase of the life cycle, or overpopulation of adults that leads to negative feedback preventing the further development of more larvae. It is advantageous for nematodes to enter arrested development as they can survive in hostile environments, cause disease in the host by a large portion of the larvae resuming development, produce large numbers of infectious eggs when the environmental conditions are once again favorable, and avoid susceptibility to various anthilmentics. The C. oncophora genome sequencing project has been recently approved for funding. The project was initially submitted by an international consortium of universities and research institutes and has been undertaken at the Washington University Genome Sequencing Center. The major goal is to aide with identification of novel target molecules for the development of new drugs and vaccines. The genomic data might prove as an invaluable resource for fundamental biological research, comparative genomics and provide new insights in genetic mechanisms involving drug susceptibility, resistance, host parasite relationships, host immunity, possibility to maintain the life of currently available drugs and improved molecular diagnostics. Recent transcriptomic data of C. oncophora from different developmental stages identified protein and domain families that are important in stage-related development. The transcriptome of C. oncopora resulted in approximately 9,600,000 reads and 29,900 assembled transcripts. These transcripts represent an estimated 81% of complete transcriptome (based on estimation from the conserved low copy eukaryotic genes). Further detailed analysis of transcriptomic data and their comparison with genomic data will provide more depth insights about parasite lifecycle and what different genes are important in the free living and parasitic stages. Excretome/secretome (ES) components essentially consist of proteins and other compounds that are secreted from the parasite and it constitutes the primary interface between parasite and host and may be further exploited as potential vaccine candidates. Analysis of the adult-stage C. oncophora ES, covered both the protein and glycan components. Several proteins were identified that have also been detected in the ES of other nematode species. Which include two different ASPs (activation- associated secreted proteins). These proteins have been shown extreme diversity in occurrence and function in prokaryotes and eukaryotes, which includes involvement in several processes like reproduction, cancer and immune regulation, though they await experimental characterization.Other proteins identified from ES fraction are aldose reductase and thioredoxin. These proteins are known to be involved in detoxification process. Innexin plays a role intercellular communication may be involved in modulating the response of anthelmintic; ivermectin. The above-mentioned findings are also consistent with transcriptomic data, showed the importance of these proteins because there transcripts were consistently observed in all C. oncophora life-stages, which further highlight their importance in parasite development. Cooperia are considered less pathogenic to livestock than other common gastrointestinal nematode worms: Haemonchus or Ostertagia. However, the pathology caused by Cooperia coupled to its wide range of distribution has huge economic impact to cattle producers. Typically calves are affected most adversely. Infection causes appetite reduction and inefficient uptake of necessary nutrients which effects body weight, reproduction and can lead eventually to calf death. Although C. oncophora does not feed on host-blood, it has the capacity to burrow through the gut wall, especially in the proximal location (duodenum) which can lead to anemia in the host.