FAO Animal Health Manual

1 FAO Animal Health ManualNo. 3 EPIDEMIOLOGY, DIAGNOSISAND CONTROL OFHELMINTH PARASITESOF SWINEA llan RoepstorffPeter NansenDanish Centre for Experimental ParasitologyThe Royal Veterinary and Agricultural UniversityCopenhagen, DenmarkFOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONSRome, 1998 The designations employed and the presentation of material in thispublication do not imply the expression of any opinion whatsoeveron the part of the Food and Agriculture Organization of the UnitedNations concerning the legal status of any country, territory, city orarea or of its authorities, or concerning the delimitation of itsfrontiers or 92-5-104220-9 All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means, electronic,mechanical, photocopying or otherwise, without the prior permission of thecopyright owner. Applications for such permission, with a statement of thepurpose and extent of the reproduction, should be addressed to the Director,Information Division, Food and Agriculture Organization of the United Nations,Viale delle Terme di Caracalla, 00100 Rome, FAO 1998 The Epidemiology, Diagnosis and Control of Helminth Parasites of SwineFOREWORDH elminth parasites of swine are ubiquitous and although no preciseinformation is available on the economic impact of these to the pigproducers, there is little doubt that they are important causingreduced feed conversion efficiency and slower weight gain.

2 Boththe commercial and the small-scale farmer continuously rank worminfections high among the Health difficulties insubstantiating the losses are associated with the fact that theinfections are chronic and less dramatic than other diseases ofswine which make these infections among the most neglected areasof veterinary care in developing addition, a fewhelminths are important in veterinary public Health , as transmissionto humans is possible through ingestion of raw- or handbook is written to assist Animal Health staff inprevention and control of these handbook, in a simple style, reviews the epidemiology ofeconomically important helminth parasites of swine and presentprocedures and techniques for their diagnosis, survey and book is designed for routine use in all types of Animal healthinstitutions, including universities, research institutes and fieldlaboratories where diagnostic parasitology is is hopedthat it will help to improve and standardize diagnostic capabilities aswell as contribute to the collection and use of basic epidemiologicaldata, the foundation for effective disease control W.

3 Hansen, ; PhDSenior Officer, ParasitologyAnimal Production and Health DivisionFAO, RomeivThe Epidemiology, Diagnosis and Control of Helminth Parasites of SwineTABLE OF CONTENTS1 THE MAJOR HELMINTH SPECIES - AN IN ORGANS/TISSUES OF THE organs and tissues6 LIFE CYCLES AND EPIDEMIOLOGY OF HELMINTH . OF THE DIGESTIVE rubidus (red stomach worm) strongylina and Physocephalus suum (large roundworm) ransomi (pig threadworm) spp. (nodular worms) suis (whipworm) nematodes of the digestive tract.. OF THE IN OTHER dentatus (kidney worm) EXAMINATIONS FOR OF FAECAL TECHNIQUES FOR FAECALEXAMINATIONS37 The Epidemiology, Diagnosis and Control of Helminth Parasites of Swine5 EXAMINATIONS FOR INFECTIVE LARVAE AND EGGS IN HERBAGE tube (Trematode eggs) TECHNIQUES FOR FAECAL McMaster McMaster the McMaster OF EGGS AND OF FAECAL EGG negative and false positive egg counts relationship between egg counts andworm burdens68 POST-MORTEM DIFFERENTIAL WORM CONTENTS OF THE STOMACH in physiological CONTENTS OF THE SMALL CONTENTS OF THE LARGE LARGE INTESTINAL LIVER AND compression pepsin-HCI digestion OF OF WORM helminth host-parasite subsample hazards109viThe Epidemiology, Diagnosis and Control of Helminth Parasites of OF HERBAGE AND SOIL OF INFECTIVE of infective larvae from of infective larvae from.

4 OF INFECTIVE EGGS FROM OF LARVAE AND EGGS1286 INVESTIGATING HELMINTH OCCURRENCE AND EPIDEMIOLOGYIN A PIG OCCURRENCE IN A MONITORING OF A EXPERIMENTS1377 CONTROL OF HELMINTHS IN PRINCIPLES OF OF or alternate of and of nutritional 'gilt-only' system for control ofStephanurus of Trichinella OF OF of an ideal drug to use RESISTANCE152 The Epidemiology, Diagnosis and Control of Helminth Parasites of and underlying of anthelmintic resistance153 Risk factors for developmentofanthelmintic of anthelmintic Epidemiology, Diagnosis and Control of Helminth Parasites of Swine1 CHAPTER 1 THE MAJOR HELMINTH SPECIES - AN abackgroundforevaluatingprevalence andimpactofhelminthosis in swine, identification of the species present in a herd,area, country or region should be investigated. Different species havedifferent pathogenic effects and bionomics. Some species areparticularly important in the young Animal , while others seem toaccumulate in the older age categories.

5 Furthermore, some speciesare relatively easy to control, while others are highly persistent in theenvironment and difficult to combat, unless more drastical measuresare the helminth spectrum in a given herd or area is alreadydefined, a status of the helminth situation should be made the first run this should be kept simple, having the primarypurpose to encircle the major species present. With this informationat hand more detailed investigations should be designed to cover themajor, relevant species in the particular herd or in the pig are relatively easy to identify if one is aware oftheir size and gross morphology and the tissues and organs in whichthey are normally located. Macroscopically visible lesions typical forsome species may provide supportive of the parasites may be based on post-mortemexamination at slaughter or when animals have died from may also be based on examination of eggs excretedwith faeces.

6 Only rarely will clinical symptoms be sufficiently specificto point to a single, responsible Epidemiology, Diagnosis and Control of Helminth Parasites of SwineThe helminths may be grouped according to their systematics(Section ) or according to their location in the pig host ( ). GROUPSThe most important helminth species, classified into major groups,are listed (redstomach worm)GnathostomaAscaris (large roundworm)Strongyloides (threadworm)Globocephalus (hookworm)TrichostrongylusOesophagostomu m (nodular worm)Trichuris (whipworm)Metastrongylus (lungworm)Stephanurus (kidney worm) (intestinal fluke)GastrodiscusOpistorchisFasciola (liver fluke)Schistosoma (blood fluke)The Epidemiology, Diagnosis and Control of Helminth Parasites of cellulosaeCysticercus tenuicollisEchinococcus IN ORGANS/TISSUES OF THE HOSTH elminths usually have typical host locations that may help isolationand identification. Adult worms in particular are confined to distinctorgans or parts of these, whereas larvae of many species may beencountered in several organs or tissues in connection with parasite identification attention should be paid to the younganimal, and animals which have not recently received anthelmintictreatment.

7 Usually pigs in the age category 2-6 months have thelargest worm burdens and may excrete many eggs with , for some specieslike Oesophagostomum spp. andHyostrongylus worm populations tend to accumulate inolderanimals. One must also bear in mind that some species have ratherlong prepatent periods, time interval between infection and startof egg excretion, for which reason faecal egg counts may benegative for a long period of time even in the presence of highparasite burdens in the host. Stephanurus, the kidney worm, has aprepatent period as long as 6-11 Epidemiology, Diagnosis and Control of Helminth Parasites of tractThe majority of worm species develops and livesindistinct,characteristic sites of the alimentary tract. In some situations theinfections are accompanied by macroscopical gut lesions, but insome cases there are no 'overt lesions even at high parasite , which are less easily identifiable, may in many instances bemore pathogenic than adults.

8 Table lists the location and effectsof the most common in different sections of the alimentary tractStomachHyostrongylusAscaropsPhysoce phalusGnathostomaSmall intestineAscarisStrongyloidesGlobocephal usTrichostrongyfusMacracanthorhynchusFas ciolopsisLarge in the liver usually produce macroscopical lesions indicativeof their migration and presence. Large transparent cysts attached tothe visceral surface of the liver will most likely show to beMucosal damageMucosal damageMucosal damageMucosa! damageAdults: mucosal changesLarvae: liver and lung lesionsMucosal damageBlood suckingMucosal damageMucosal damageMucosal damageMucosal damage, nodulesBlood suckingMucosal damageSiteHelminthEffectsThe Epidemiology, Diagnosis and Control of Helminth Parasites of Swine5 Cysticercus tenuicollis, the metacestode of Taenia hydatigina (a dogtapeworm). Deeper, partially superficial cysts may be metacestodes -socalled hydatids of Echinococcus granulosis, also a dog tape lesions (tracts) in the parenchyma may be caused byimmature Fasciola and Cysticercus tenuicollis larvae.

9 Ascaris andSchistosoma produce fibrotic or granulamatous lesions, typical foreach of these helminths. Following incision adult Fasciola may beobserved and collected from the bile Helminths in the liverHelminthEffectAscaris (larvae)Fibrotic lesions: "white" or "milk"spotsSchistosoma (eggs)Fibrosis, granulomasFasciola (larvae, adults)Fibrosis, bile duct enlargement. BloodsuckingCysticercus tenuicollis (metacestodes)Tissue damage, fibrosisEchinoccocus granulosusPressure atrophy(metacestodes: hydatid cysts) most important helminths that invade the lung are the piglungworms, of which there are three common species belonging toMetastrongylus. These are primarily found in the bronchioli. Inaddition, Ascaris larvae pass the lung as part of their host migration -and may produce traumatic lesions. Hydatid cysts may occasionallyI observed in the lung Epidemiology, Diagnosis and Control of Helminth Parasites of SwineTABLE Helminths in the lungHelmmthEffectMetastrongylusBronchiti s, pneumoniaAscarisTraumatic lesionsHydatid cystsTissue organs and tissuesHelminths may be found ina number of tissues outside thealimentary tract, liver and lungs.

10 Accidental findings may simplyreflect aberrant migration of parasites belonging to the above , other parasites have primary, natural predilection sites, in muscle tissue and in the kidney, see Table 1 .4 Helminths in various organsMuscleKidneyTrichinella (larvae)MinimalCysticercus cellulosaeMinimalStephanurusDamage, moderateBlood vesselsSchistosomaIntestinal and hepaticdamageSiteHelminthEffectsThe Epidemiology, Diagnosis and Control of Helminth Parasites of Swine7 CHAPTER 2 LIFE CYCLES AND EPIDEMIOLOGY OF HELMINTH chapter primarily describeslifecycles, epidemiology andpathogenecity of those helminths having highest prevalences andgreatest economic impacts. The description therefore mainlycomprises the helminths listed in Chapter 1 (Sections 1 .. ,Tables 1 .1-1 .4). A more comprehensive list of helminths in pigs, withfocus on life cycles, transmission and host relationships will be foundat the end of the present chapter (Tables and ).