Epidemiological Investigation Of Gastrointestinal Nematodiasis In Sheep And Preliminary Study On Its Biocontrol With Nematophagous Fungi In The Eastern Inner Mongolia In China

Gastrointestinal nematode is a generic term for a variety of Nematoda nematodes parasitic in the alimentary tract of the host,mainly in the esophagus,stomach,duodenum,jejunum,ileum,colon,cecum and rectum of humans and animals.It can cause extensive damage to the host.They include:seizing nutrition,taking blood,destroying mucosal tissue,physical oppression,blocking pipelines,releasing toxins,causing allergic reactions,triggering inflammation,inducing immune deficiency and introducing other pathogens.Gastrointestinal nematodiasis is the main parasitic disease in the world,which is distributed globally and widely spread.Many animals can be infected,causing serious economic losses and public health threats.Ovine gastrointestinal nematodiasis is mainly caused by the infections of Trichurata,Rhabditata and Strongylata nematodes,which are of many species,widely distributed and mixed infections.The gastrointestinal nematode infection of grazing sheep in grassland is particularly serious,mainly caused by soil-borne nematodes.It can result in low conversion rate of sheep forage,increased breeding cost,slow weight gain,stunted growth,prolonged growth cycle,reduced reproductive performance,decreased immunity and low economic efficiency,which restrict the healthy development of sheep industry.Regular expelling parasite use of chemical drugs is still the main method of prevention and treatment of gastrointestinal nematodiasis of sheep.The long-term and frequent application of chemical anthelmintic,especially the nonstandard types,routes,doses and times of administration,lead to the emergence of drug-resistant strains.The emergence of anthelmintic resistance?AR?has become a global problem plaguing the sheep industry.The development of new anti-gastrointestinal nematode drugs and the in-depth study of gastrointestinal nematode biological control technology are imminent.The stock of sheep in the Eastern Inner Mongolia has remained at about 60 million in recent years,accounting for more than 70%of the total stock of sheep in the Inner Mongolia.The Eastern Inner Mongolia has a usable grassland area of about 38 million hectares.It is an important grassland animal husbandry production base in the Inner Mongolia.In recent years,sheep industry has shown a good and stable development momentum.In order to understand the infection of gastrointestinal nematode in sheep under grazing conditions in the Eastern Inner Mongolia,to make clear the resistance of gastrointestinal nematode to common chemical drugs,and to find new ways of biological control.In this study,five cities in the Eastern Inner Mongolia which have the advantage of sheep industry development,were selected as research areas,and 10 representative counties were selected as survey sites,and grazing sheep were taken as research objects.The collection of gastrointestinal nematode eggs from sheep feces was carried out by saturated saline flotation method.The detection and counting of gastrointestinal nematode eggs in sheep feces were carried out by McMaster's method,and the infection rate and intensity of gastrointestinal nematode were determined.The species identification of gastrointestinal nematode eggs was carried out by comparing with the Oocyte Atlas of Sheep Parasitic Helminth.The incubation test of third-stage larvae?L3?of dominant gastrointestinal nematode in grazing sheep was carried out according to the current agricultural industry standard NY/T1465-2007,and the identification of gastrointestinal nematode infection species was completed.The parasitic sites of gastrointestinal nematode in sheep were dissected,the adult of gastrointestinal nematode was detected,and the pathological damage of the parasitic tissues was detected and analyzed.The epidemiological status of gastrointestinal nematode in sheep in the Eastern Inner Mongolia was investigated,and the AR of gastrointestinal nematode to traditional anthelmintic was evaluated.The isolation,culture and molecular identification of nematophagous fungi were carried out from the soil of survey sites,and the experiment of nematophagous fungi killing gastrointestinal nematode was carried out.Results:The highest infection rate of gastrointestinal nematode was 100%,the lowest infection rate was 45%,and the average infection rate was 79.2%.The highest infection intensity of individuals infected with gastrointestinal nematode in grazing sheep was 32400EPG,and the highest infection intensity was 6192.5 EPG,and the lowest infection intensity was494.1 EPG.The average infection intensity in the Eastern Inner Mongolia was 1813.2 EPG.The types of gastrointestinal nematode infected by grazing sheep were complex and varied,and the infection was serious.More than 30 different forms of gastrointestinal nematode eggs and10 unknown eggs were detected.The main types of gastrointestinal nematode infected were Trichostrongylus spp.,Haemonchus spp.,Ostertagia spp.,Nematodirus spp.and Strongyloides spp.,among which Haemonchus spp.and Trichostrongylus spp.were the most infected.Gastrointestinal nematode infection in grazing sheep may be different in different regions,breeds,sexes and ages.Gastrointestinal nematode can cause severe pathological damage to the parasitic sites of sheep,causing many mechanical injuries and inflammatory reactions such as edema,congestion,bleeding,ulcer,erosion,thickening,atrophy,defect,abscission and so on.A large number of eosinophils infiltration can be seen microscopically.In the Eastern Inner Mongolia,sheep gastrointestinal nematode showed significant resistance to avermectin,ivermectin and albendazole,especially to albendazole.The ED₅₀ value of albendazole to sheep gastrointestinal nematode reached 5.670?g/mL.AR strains include Haemonchus spp.,Trichostrongylus spp.and Strongyloides spp.nematode,the most important of which is Haemonchus spp..Two nematode-trapping fungi were isolated from the soil of the Eastern Inner Mongolia,and identified by ITS sequence as Papiliotrema flavescens and Rhizopus oryzae strains,which provided theoretical basis for clinical biological control of gastrointestinal nematode in sheep.These spore preparation can effectively reduce the number of gastrointestinal nematode eggs in sheep feces,which needs further experimental verification.The results showed that the infection of gastrointestinal nematodiasis of sheep in the Eastern Inner Mongolia was serious,and the resources of nematophagous fungi were abundant in the area.This study provides the latest survey data for the current situation of gastrointestinal nematodiasis infection in sheep in the Eastern Inner Mongolia,provides theoretical basis and technical support for the biological control of gastrointestinal nematode.