PRESENTATION BROCHURE Atlas of parasites in sheep Elias Papadopoulos
Atlas of parasites in sheep Atlas of parasites in sheep Atlas of parasites in sheep Elias Papadopoulos AUTHOR: Elias Papadopoulos. FORMAT: 22 x 28 cm. NUMBER OF PAGES: 128. NUMBER OF IMAGES: 310. BINDING: hardcover. RETAIL PRICE 68 ebook included Atlas entirely dedicated to the most important parasites and parasitic diseases of sheep, and written by a prestigious specialist in Parasitology with a wide experience in this species. More than 300 high-quality images have been included to show, among other things, the main parasites (protozoa, helminths and arthropods) infecting sheep, providing identification features to clearly distinguish between species, as well as the principal clinical signs derived from each infection / infestation. Each chapter has been dedicated to a specific anatomic system of sheep. Besides, two additional chapters focused on the most commonly used parasitological methods and antiparasitic drugs have been included to complement the information provided. The atlas is aimed at clinicians, laboratory diagnosticians, researchers, students, etc., and its format helps to make the contents more understandable and accessible to readers.
Atlas of parasites in sheep Presentation of the book This Atlas of Parasites in Sheep has been prepared and presented in the hope to become a useful tool for the diagnosis and control of the most common parasitic diseases of sheep around the world. Thorough knowledge of parasitic infections of sheep is a basis for the prevention of many diseases of these animals, as well as of other species and humans. The One Health approach has become important in view of the great significance of the zoonotic parasites and the role which veterinarians can play in their prevention. The book is intended to be used by those involved in addressing problems of sheep health. It may be used by clinicians, laboratory diagnosticians and researchers alike, veterinarians or other professionals, as well as by students; it will also provide information to interested professional or hobby sheep farmers. Readers should bear in mind that material included was necessarily selective in its detail. It was avoided to provide an extensive overview, as in principle, this book has been prepared to become a supplement to other textbooks related to sheep diseases. The parasitic fauna discussed in this book includes all parasites that may infect sheep (protozoa, helminths and arthropods). Their presentation is according to the organ they can infect. Each chapter is dedicated to a specific anatomic system of sheep (i.e., gastrointestinal, reproductive, respiratory, other systems) and is preceded by a short introduction. Each parasite is presented under the same format, including its latin and common name, taxonomy, location(s) within the host, geographical distribution, morphology, pathogenesis and clinical signs, diagnosis, control and public health. An additional chapter, which includes the most commonly used parasitological methods, provides technical information to support laboratory diagnosis of parasitic diseases. Finally, a chapter with the antiparasitic drugs and their mode of administration completes the book. Elias Papadopoulos
Atlas of parasites in sheep The author Elias Papadopoulos Graduated (DVM) in 1988 from the Faculty of Veterinary Medicine, Aristotle University of Thessaloniki (Greece). Master in Veterinary Science (MSc) degree in Veterinary Parasitology in 1992 from the University of Liverpool (UK). PhD degree in 1997 from the Faculty of Veterinary Medicine, Aristotle University of Thessaloniki. He is Professor and Head of the Laboratory of Parasitology and Parasitic Diseases at the School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki. He has received training on parasitology in established European research centers and Universities. He has participated in several national and international research projects, published papers and delivered lectures in national and international scientific conferences. hkeita/shutterstock.com
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Atlas of parasites in sheep Elias Papadopoulos
Table of contents 1. Gastrointestinal system Oesophagus Gongylonema pulchrum (gullet worm) Rumen/Reticulum Paramphistomum spp. (rumen fluke) Abomasum Haemonchus contortus (barber s pole worm) Teladorsagia spp. Small intestine Cryptosporidium spp. Eimeria spp. Giardia spp. Trichostrongylus spp. Nematodirus spp. Cooperia curticei Bunostomum trigonocephalum Strongyloides papillosus Moniezia expansa/moniezia benedeni Large intestine Liver Tetratrichomonas ovis Oesophagostomum spp. Chabertia ovina Skrjabinema ovis (pinworm) Trichuris ovis (whipworm) Fasciola hepatica (liver fluke) Dicrocoelium dendriticum (small fluke) Cysticercus tenuicolis Hydatid cyst Linguatula serrata 2. Respiratory system Nasal cavities Oestrus ovis (sheep nasal bot) Limnatis nilotica (aquatic leeches) Lungs (trachea - bronchi - lung tissue) Dictyocaulus filaria (sheep lungworm) Protostrongylus rufescens (red lungworm) Muellerius capillaris (nodular lungworm) Cystocaulus ocreatus (small lungworm) Neostrongylus linearis (red lungworm) Hydatid cyst 3. Reproductive system Uterus - placenta Toxoplasma gondii 4. Circulatory system Blood Trypanosoma spp. Babesia spp. Theileria spp. 5. Locomotory system Muscles Sarcocystis ovicanis Sarcocystis ovifelis Toxoplasma gondii Cysticercus ovis (sheep measles, ovine cysticercosis)
6. Nervous system Brain - spinal cord Coenurus cerebralis (gid) Toxoplasma gondii 7. Integumentary system Class Arachnida Ticks Mites Sarcoptes scabiei (sarcoptic mange) Psoroptes ovis (psoroptic mange) Chorioptes ovis (chorioptic mange) Demodex ovis (demodectic mange) Psorergates ovis Neotrombicula spp. (harvest mite) Class Insecta Flies causing traumatic myiasis (fly strike) Flies causing obligatory myiasis (nasal bots) Other flies (causing nuisance and bloodfeeding) Simulium spp. (blackflies) Culicoides spp. (biting midges) Tabanus spp. (horseflies) Melophagus ovinus (keds) Lice Fleas 8. Laboratory diagnostic methods Faecal examination Collection and preservation of faeces Faecal examination methods Direct smear method (wet preparation) Flotation method Sedimentation method Stained faecal smear for Cryptosporidium spp. oocysts detection (modified Ziehl-Neelsen) method Faecal antigen detection McMaster method FLOTAC method Coproculture Baermann method Pasture herbage examination Blood examination Thin blood smears Serology Skin examination Molecular methods Anthelmintic resistance methods Faecal egg count reduction test (FECRT) Egg hatch test (EHT) Larval development test (LDT) 9. Antiparasitic drugs Groups and mode of action Antiprotozoals Ionophores Quinolones Symmetrical triazinones Thiamine antagonists Quinazolines Anthelmintics Macrocyclic lactones Benzimidazoles and pro-benzimidazoles Imidazothiazoles Tetrahydropyrimidines Pyrazinoisoquinolines Salicylanilides Substituted phenols Amino-acetonitrile derivatives Spiroindoles Insecticides/acaricides Macrocyclic lactones Organophosphorus compounds Formamidines Synthetic pyrethroids Routes of administration References
Atlas of parasites in sheep Abomasum HAEMONCHUS CONTORTUS (BARBER S POLE WORM) The most common species is Haemonchus contortus, but other species have also been reported in sheep, as Haemonchus placei. Taxonomy Class Nematoda, Superfamily Trichostrongyloidea. Location Abomasum. Geographical distribution Worldwide, particularly in tropical and subtropical areas. Morphology The adult worms are very easily identified due to their location, large size (2-3 cm) and the characteristic appearance of the white ovaries around the red (blood) filled intestine of the worm (fresh specimens) (Figs. 8-12). Infective larvae have a medium size tail-sheath distance with narrow head (Figs. 13 and 14). Eggs are typical of the Trichostrongyloidea Superfamily (ellipsoidal or barrel-shaped and smooth surfaced with numerous blastomeres) (Figs. 15 and 16). FIGURE 8. Haemonchus contortus body with ovaries winding spirally around intestine. Pathogenesis and clinical signs It is a blood-feeding parasite and, in large numbers, may cause haemorrhagic anaemia, weight loss, weakness and death (Fig. 17). Each worm can obtain approximately 0.05 ml of blood per day from the mucosal vessels and therefore, in heavy parasitism, the haematocrit falls progressively (Fig. 18). Depending on the parasite burden, haemonchosis may be presented as hyperacute, acute or chronic form. The life cycle is direct and sheep become infected by ingesting the infective third-stage larvae (L3) with the herbage (Fig. 19). Female worms are prolific egg layers contaminating the pasture. Eggs develop and L1 hatch in a week, depending on the temperature (in cooler environment this may take place after several weeks or months) (Fig. 20). Adult worms can move on the surface of the abomasum mucosa. Diagnosis It is based on faecal examination, particularly using a quantitative coprological method (i.e. the modified McMaster method), in order to estimate the number of eggs per gram of faeces. However, as in practise mixed infections with other trichostrongylids are common, a coproculture is necessary to be performed in order to identify the L3 of Haemonchus spp. Necropsy can give a clear picture of the worm burden (Fig. 21). PCR may be used for larvae identification, which is of limited use in the field practice at the moment. Control Sheep may be treated effectively with most of the anthelmintic groups, such as benzimidazoles, levamisole or macrocyclic lactones. It is important, additionally to adult worms, to remove the hypobiotic larvae. The use of anthelmintics should be combined with the pasture management. In milk-producing ewes, the residual withdrawal periods in milk should be kept into consideration, whereas in wool-producing animals this is not a case. In most areas of the world, anthelmintic resistant strains of Haemonchus spp. have been developed reducing the effectiveness of treatments. In order to reduce the rate of the development of anthelmintic resistance, several strategies have been introduced to sheep industry, taking into consideration the balance of the worms coming in contact with the drugs or remain at 4
GasTRoinTesTinaL system abomasum 1 FIGURE 9. Haemonchus contortus posterior end of female. FIGURE 10. Haemonchus contortus head of female. FIGURE 11. Haemonchus contortus cervical papillae (adult anterior end) (arrows). FIGURE 12. Haemonchus contortus adult female: vulval flap. FIGURE 13. Second-stage larva of Haemonchus contortus: the larva s body and the second-stage sheath (posterior end) may be observed. FIGURE 14. Second-stage larva of Haemonchus contortus: the bolbous (anterior end) oesophagus may be observed (arrow). 5
Atlas of parasites in sheep FIGURE 15. Trichostrongyle egg. FIGURE 16. Trichostrongyle eggs and larvae L1. FIGURE 17. Weak sheep. FIGURE 18. Ewe with heavy gastrointestinal parasitism and low body condition score. FIGURE 19. Green pasture. FIGURE 20. Nematode larva (L1) hatching from egg. 6
GasTRoinTesTinaL system abomasum 1 FIGURE 21. Haemonchus contortus adult worms in the abomasum mucosa. pasture (in refugia). Most of them aim to the reduction of anthelmintic usage and the rotation of different drug classes (with different mode of action). Towards this end, strategic programmes are based on the Targeted Treatments (administration of anthelmintics to all the animals of the flock according, for example, to their reproduction phase, i.e. at tupping or lambing) or the Targeted Selected Treatments (administration of anthelmintics only to certain animals within the flock that are in need based on selection criteria, i.e. faecal egg counts, body condition score, milk yield and others). Particularly for haemonchosis, the Famacha system has been developed to enable the detection of infected sheep according to the colour of their mucous membranes, which reflects the level of anaemia due to parasitism. Recently, the use of vaccines has been introduced against Haemonchus spp. infection. Public health No reports. TELADORSAGIA SPP. The most important is Teladorsagia circumcincta, but other species also occur as Ostertagia trifurcata, Teladorsagia davtiani, etc. Taxonomy Class Nematoda, Superfamily Trichostrongyloidea. Location Abomasum. Geographical distribution Worldwide. Morphology The adult worms are small (approximately male: 6-8 mm, and female: 8-10 mm), slender with a short buccal cavity (Figs. 22 and 23). Infective larvae (L3) have a short size 7
Atlas of parasites in sheep a a b b c c FIGURE 22. (a) Teladorsagia circumcincta female. Detail of the (b) head and (c) posterior end. FIGURE 23. (a) Teladorsagia circumcincta male worm. Detail of the (b) head and (c) posterior end. 8
GasTRoinTesTinaL system abomasum 1 a tail-sheath distance (Fig. 24). Females lay typical trichostrongyle eggs (Figs. 25 and 26). The species identification of the adults is based on the morphology of the bursa and spicules (Fig. 27). Pathogenesis and clinical signs Infected sheep show reduced appetite, weight loss and loss of plasma protein into the gastrointestinal tract (Fig. 28). The life cycle is direct and sheep become infected by ingesting the infective L3 with the herbage. Ingested larvae enter the gastric glands and destroy them. In necropsy of heavily infected animals, the abomasal surface looks like morocco leather (Fig. 29). b Diagnosis It is based on the clinical signs, but confirmed with coprological examinations and necropsy, as in haemonchosis or other trichostrongylids. Control It is based on the strategic use of effective anthelmintics, as described in haemonchosis. Public health No reports. In sheep abomasum may also exist the nematode Marshallagia marshalli (Superfamily Trichostrongyloidea), which is found in certain areas, including India and Russia. c FIGURE 24. (a) Teladorsagia circumcincta L3 (-b- anterior and -c- posterior part). FIGURE 25. Trichostrongyle egg. 9
Atlas of parasites in sheep FIGURE 26. Teladorsagia circumcincta female worm with eggs. FIGURE 27. Teladorsagia circumcincta male worm with bursa and spicules. FIGURE 28. Poor clinical picture. FIGURE 29. Characteristic lesions on abomasum mucosa due to infection with Teladorsagia circumcincta. 10
GasTRoinTesTinaL system small intestine 1 Small intestine CRYPTOSPORIDIUM SPP. Taxonomy Subphylum Apicomplexa, Family Cryptosporidiidae, Genus Cryptosporidium parvum and others. Location Cryptosporidium spp. is a protozoan parasite infecting the microvillus borders of the enteric epithelial cells. and coproantigen-based diagnostic methods can also be used. Finally, molecular methods (genotyping) can be used to characterise the Cryptosporidium species. Geographical distribution Worldwide. Morphology Oocysts are spherical 4.0-8.0 μm in diameter. Development is intracellular, but extracytoplasmic in a parasitophorus vacuole. Oocysts contain four sporozoites (without sporocysts) and sporulation takes place within the host, so that the oocysts are immediately infective. Pathogenesis and clinical signs It has been shown that two types of oocysts are produced, the thick-walled (majority), that are passed out with the faeces, and the thin-walled (minority), that release their sporozoites inside the intestine causing auto-infection. The main route of infection is by the direct animal-to-animal faecal-oral route. In young lambs (2-14 days old), it occurs during coprophagy, suckling milk from dirty udders or buckets and by faecal soiling (Fig. 30). In lambs, infection appears to be age-related with seasonal peaks following the birth peaks in spring and autumn. Chilling due to adverse weather conditions in the neonatal period, intercurrent infections (i.e. Escherichia coli or rota/corona viruses) or nutritional-mineral deficiencies could increase the likelihood of disease. The symptoms include anorexia and persistent diarrhoea (Fig. 31), and in case that immunity fails to develop, then death is common. Diagnosis The diagnosis is done by demonstration of oocysts in the faeces by staining faecal smears using the Ziehl-Neelsen stain, where the sporozoites appear as bright red granules (Fig. 32). Serology FIGURE 30. Lambs feeding from faecal contaminated equipment. FIGURE 31. Lambs with diarrhoea due to Cryptosporidium spp. infection. 11
Atlas of parasites in sheep Control Treatment and prevention is based on the use of available drugs, particularly effective being the halofuginone lactate, combined with supportive therapy (rehydration, antibiotics, etc). Appropriate colostrum supply is of great importance to avoid cryptosporidial diarrhoea. Besides, animals with massive oocyst excretion should be separated from the others. Oocysts remain viable for months and are resistant to many disinfectants, therefore regular removal of the contaminated faecal material is strongly recommended. FIGURE 32. Cryptosporidium spp. oocysts in stained faecal smear. Public health Sheep cryptosporidiosis may be of zoonotic importance depending on the Cryptosporidium species involved. Proper care should be taken for immune-deficient individuals (i.e. AIDS patients). EIMERIA SPP. Several (more than 11) Eimeria species occur in sheep, such as Eimeria crandallis, Eimeria ovinoidalis, Eimeria ahsata, Eimeria bakuensis, Eimeria faurei, Eimeria granulosa, Eimeria gilruthi and others. Taxonomy Class Sporozoasida, Family Eimeriidae. Location Abomasum: Eimeria gilruthi. Small intestine: Eimeria ahsata, Eimeria bakuensis, Eimeria faurei, Eimeria granulosa and others. Large intestine: Eimeria crandallis, Eimeria ovinoidalis. Geographical distribution Worldwide. FIGURE 33. Eimeria oocyst (black arrow) and Dicrocoelium egg (white arrow). Morphology Eimeria spp. oocysts differ morphologically (and genetically) basically according to size, shape, presence or absence of polar cap, colour and oocyst residuum (Fig. 33). For example, Eimeria ahsata oocyst is ovoid (33.4 22.6 μm) with distinct polar cap, without oocyst residuum and of yellow brown colour; Eimeria parva oocyst is spherical (16.5 14 μm) without oocyst residuum and colourless. Unsporulated oocysts consist of a wall that encloses a nucleated mass of protoplasm. Under suitable conditions (increased temperature, humidity and oxygen), the oocyst sporulates to form four sporocysts containing two sporozoites each (infective form, sporulated oocyst) (Fig. 34). 12
GasTRoinTesTinaL system small intestine 1 Pathogenesis and clinical signs Several Eimeria species have been identified in sheep according to morphologic and genetic characteristics, however only Eimeria ovinoidalis and Eimeria crandallis are considered to be highly pathogenic. The rest are not pathogenic, with the exception of Eimeria gilruthi, which is possibly associated in high numbers with abomasitis, anorexia and diarrhoea. The life cycles are typical coccidian. Sheep become infected by the ingestion of the sporulated oocysts, which follow merogony and gametogony into the small intestine in order to produce oocysts, which are passed with the faeces. Sporogony takes place at the environment depending on the temperature and humidity in 2-4 days. The animals most at risk are lambs at weaning in grazing pens or when placed in feedlots (Fig. 35). Clinical signs vary from anorexia, weight loss, pasty to watery diarrhoea (with or without blood), tenesmus and dehydration (Fig. 36). The intestine may become thickened and oedematous with petechiae and haemorrhages (Fig. 37). Clinical coccidiosis is expected to occur after shipping or any other stress factor. Diagnosis The diagnosis is made by the clinical signs and the farm history, faecal examination (flotation), though could be misleading as several Eimeria species are not pathogenic. Post-mortem findings, particularly small irregular whitish raised lesions, combined with scrapings may give a more reliable diagnosis (Fig. 38). a b FIGURE 34. (a) Sporulated and (b) non sporulated Eimeria. Control Administration of anticoccidial drugs (chemical, i.e. diclazuril, decoquinate, sulphonamids), colostrum and good hygienic conditions are essential to control coccidiosis (Figs. 39 and 40). Exposure to oocysts or any stressful condition should be minimised (Fig. 41). Recently, plant origin supplements claim to contribute effectively to the coccidian control. It is often a good strategy to start the treatment before lambs are moved to a contaminated feedlot or grazing pen. The development of immunity is of significant importance for the lamb survival. Eimeria spp. have a strong host specificity and therefore lambs become infected only from ovine Eimeria species, as no cross-contamination exists, even without the goat Eimeria species. Public health No reports. FIGURE 35. Clean pen for keeping lambs at low risk for parasite infection. 13
Atlas of parasites in sheep FIGURE 36. Diarrhoea due to gastrointestinal parasitism. FIGURE 37. Intestine infected with Eimeria spp. FIGURE 38. Small intestine infected with Eimeria spp. FIGURE 39. Clean pen for keeping ewes at low risk for parasite infection. FIGURE 40. Lambs receiving colostrum. FIGURE 41. Lambs kept on clean warm pen. 14
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