Parasitology
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VETERINARY PARASITOLOGY SECOND EDITION G M URQUHART J ARMOUR J L DUNCAN A M DUNN F W JENNINGS Veterinary Parasitology Second Edition G. M. Urquhart J. Armour J. L. Duncan A. M. Dunn F. W. Jennings The Faculty of Veterinary Medicine The University of Glasgow Scotland Blackwell Science CONTENTS Foreword to thefirst edition vii Suhorder CYCLORRHAPHA Acknowledgements to the first edition ix Family MUSCIDAE Foreword and acknowledgements lo the seco,zd Family CALLIPHORIDAE edition xi Family SARCOPIIAGIDAE Family OESTRIDAE VETERINARY HELMINTHOLOGY Family HIPPOBOSCIDAE Order PHlHlRAmERA Phylum NEMATHELMINTNES 3 Suhorder ANOPLURA Class NEMATODA 4 Suborder MALLOPHAGA Superfamily TRICHOSTRON(iYLO1DEA 10 Order SIPHONAPTERA Superfamily STRONCYLOIDEA 42 Class ARACHNIDA Superfamily MBI'ASI'KONGYLOIDEA 57 Order ACARINA Superfamily RHABUSIOIDEA 65 Family IXODIDAE Superfamily ASCARIDOIDEA 67 Family AKGASIDAE Superfamily OXYUROIDEA 77 Family SARCOPTIDAE Superfamily SPIRUROIDEA 79 Family DEMODICIDAE. Superfamily FlI.ARIOIDEA 85 Family 1.AMINOSIOPSIDAE Superfamily TRICHUKOIDEA 95 Family PSOKOYIIUAE Superfamily DIOCTOPHYMATOIDEA 99 Family CHEYLETIDAE Phylum ACANTHOCEPHALA 100 Family DERMANYSSIDAE Phylum PLATYHELMINTHES 1 02 Class PENTASTOMIDA Class TREMATODA 102 Subclass DlGRNRA 102 VETERINARY PROTOZOOLOGY Family FASCIOLIUAC: 103 Family DICROCOELIIDAE 113 Phylum PROTOZOA Family PARAMPHISTOMATIDAE 115 Subphylum SARCOMASI'ICOPHORA Family TROGLOTREMAIIDAE 116 Class SARCODINA Family OPISTHORCHIIDAR 117 Class MASTIGOPHORA Family SCHISTOSOMATIDAE 117 Subphylum SPOROZOA Family DIPLOSTOMAIDAE 120 Class COCCIDIA Class CESTODA 120 Family RIMERIIDAE Order CYCLOPHYLLIDEA 120 Pamily SAKCOCYSnUAE Family TAENIIDAE 122 Class P~KOPLASMIDIA Family ANOPLOCEPHAIIDAC 130 Class HAEMOSPORIDIA Family DILEPIDIDAE 133 Subphylum CILIOPHORA Family DAVAlNElDAE 135 Subphylum MICROSPORA Family HYMENOLEPIUIDAE 136 Order RICKETISIALES Family MESOCESTOIDIDAE 136 Family THYSANOSOMIDAE 136 REVIEW TOPICS Order PSEUDOPIIY1.LIDEA 137 The epidemiology ofparasitic diseases VETERINARY ENTOMOLOGY Resistance to parasitic disea,es Anthelmintics Ectoparasiticides (insecticides/acaricides) Phylum ARTHROPOUA 14' The luboratory diagnosi.~ofparasitism Class INSECI'A 142 Order DlflERA 143 Suborder NEMATOCERA 145 HOST/PARASITE LISTS Family CERATOPOGONIDAE 145 Family SIMULIIDAE 146 Sources of further information Family PSYCHODIUAE 147 Family CULlClUAE 148 Index Suborder BRACHYCERA 151 Family TABANIDAE VETERINARY HELMINTHOLOGY PRINCIPLES OF CLASSIFICATION Thc names oI taxa must be adhered to according to the international rules, but it is permissible to anglicize All animal organisms are relatcd to one another, the endings, so that members of the supcrfamily closely or remotely, and the study of the complex sys- Trichostrongyloidea in thc example above may also be tems of inter-relationship is called systematics. It is termed trichostronevloids.L., essentially a study of the evolutionary process. The names of the genus and species are expressed in When organisms are examined it is seen that they Latin form.. the -eeneric name havine a cauital letter, form natural groups with features, usually morpho- and they must be in grammatical agreement. It is cus- logical, in common. A group of this sort is called a tomary to print foreign words in italics, so that the taxon, and the study of this aspecl of biology is called name of an organism is usually underlined or itali- taxonomy. cized. Accents are not permitted, so that, if an organ- The taxa in which organisms may be placed are ism is named aftcr a person, amendment may he recognized by international agreement, and the chief neccssary; the name of Miiller, for example, has been oncs are: kingdom, phylum, class, order, family, genus altered in the genus Muellerius. and species. The intervals between these arc large, and The higher taxa containing helminths of veterinary some organisms cannot be allocated to them precisely, importance are: so that intermediate taxa, prefixed appropriately, have been formed; examples of these are the suborder Major and the snperfamily. As an instance, the taxonomic Nemathelminthes (roundworms) status of one of the common abomasal parasites of Platyhelminthes (flatworms) ruminants may he expressed as shown below. Minor Acanthocephala (thornyhcaded worms) Kingdom Animalia Phylum Nemathelminthes Class Nematoda Order Strongylida Though the phylum Nemathelminthes has six classes Suborder Strongylina only one of these, the nematoda, contains worms of Superfamily Trichostrongyloidea parasitic significance. The nematodes are commonly Family Trichostrongylidae called roundworms, from their appearance in cross- Subfamily Haemonchinae section. Genus Iluvmonchus Species conlorlus 4 Veterinary Parasitology Table 1 Paras I c Nematooa of velerlnary mponance PA sfmD Ieo c asslflcar on A system of classification of nematodes of veterinary importance is given in Table 1. Superfamily Typical features It must bc emphasized that this is not an exact ex- pression of the general system for parasitic nema- Bursate nematodes todes, hut is a simplified presentation intended for use in the study of veterinary parasitology. It is bascd on Trichostrongyloldea Buccal capsule small. the ten superfamilies in which nematodes of vetcri- Trichostrongyius, Life cycle direct; infection nary importance occur, and which are conveniently Osteftagia, Dicfyocaulus, by L,. divided into bursate and non-bursate groups as shown Haemonchus, etc. in Table 1. Strongyloidea Buccal capsule well Strongylus, Ancylostoma, developed; leaf crowns STRUCTURE AND FUNCTION Syngamus, etc. and teeth usually present. Life cycie direct; infection Most nematodes have a cylindrical form. taoerine at hv I "7 T either end, and the body is covered by a colour~ss, somewhat translucent, layer, the cuticle. Metastrongyloidea Buccal capsule small. The cuticle is secrctcd by the underlying Mefastrongyius, Life cycle indirect; hypodermis, which projects into the body cavity form- MUellerius, infection by L, in ing two lateral cords, which carry the excretory canals, PrOfDStrongylus, intermediate host. and a dorsal and ventral cord carrying the nerves (Fig. 1). The muscle cells, arranged longitudinally, lie be- tween the hypodemis and the body cavity. The latter contains fluid at a high pressure which maintains the RhabditOidea Very small worms; buccal turgidity and shape of the body. Locomotion is ef- StrD"9Y10ides, Rhabdifis, capsule small. Free-living fected by undulating waves of muscle contraction and and parasitic generations. relaxation which alternate on the dorsal and ventral Life cycle direct; infection aspects of the worm. by L. Most of the internal organs are filamentous and ~~~~~id~id~~Large white worms. suspended in the fluid-filled body cavity (Fig. 2). Ascaris. Toxocara, Life cycle direct; infection The digestive system is tubular. The mouth of many pamcarisris,etc. by L, in egg. nematodes is a simple opening which may be sur- rounded by two or three lips, and leads directly into OxYuroidea Female has long, pointed the oesophagus. In others, such as the strongyloids, it OxYUris, Skqabinema,etc. tail. is large, and opens into a buccal capsule, which may Life cycle direct; infection contain teeth; such parasites, when feeding, draw a by L, in egg. plug of mucosa into the buccal capsule (Fig. 3), where spiruroidea Spiral tail in male. Spirocerca, Habronema, Life cycle indirect; Thelazia, etc. infection by L, from insect. Filarioidea Long thin worms. Dorsal nerve Dirofilaria, Onchomrca, Life cycle indirect; Cuticle Parafilaria, etc. infection by L, from Ovaw insect. Trlchuroidea Whip-like or hair-like Intestine Excretow THchuHs, Capillaria, worms. Uterus Trichineiia, etc. Life cycle direct or Muscle indirect; infection by L,. HvP~~~~~~~Dioctophymatoidea Very large worms. ventralnerve Dioctophyma, etc. Life cycle indirect; infection by L, in aquatic annelids. Flg. 1 Transverse section of i. typical nematode Veterinary Helminthology 5 Nerve ring Oesophagus Intestine Rectum The oesophagus is usually muscular and pumps 1 I food into the intestine. It is of variable form (Fig. 4). and is a useful preliminary identification character for groups of worms. It may be filariform, simple and slightly thickened poslcriorly, as in the hursate nema- todcs; bulb-shaped, with a large posterior swelling, as in the ascaridoids: or douhlehulb-shaned.. , as in-the oxyuroids. In some groups this wholly muscular fonn does not occur: the filarioids and spiruroids have a muscular-glandular ocsophdgus which is muscular (bl anteriorly, thc posterior part being glandular: the ray trichuroid oesophagus has a capillary form, passing through a single column of cells, the wholc bcing known as a stichosome. A rhabditifnrm oesophagus, with slight anterior and postcriur swellings, is present in the preparasitic larvae of many nematodes, and in adult free-living nematodes. Fig. 2 Longitudinal sections of a nematode illustrating: (a) Diges- ~h,intestine is a tube ,,,hose lumen is enclosed by a tive, excretory and nervous system: (b) Reproductive system of female and male nematodes. singlc layer ol cells or by a syncytinm. Their lumiual surfaces nossess microvilli which increase thc absorn- tive capacity of the cells. In female worms the intestine terminates in an anus whilc in males there is a cloaca which functions as an anus, and into8 which opens the vas deferens and lhrough which the copulatory spiculcs may be extruded. Fig. 3 Large buccal capsule of strongyloid nematode ingesting plug 01 mucosa. Rhabditiform