Superfamily: Trichostrongyloidea

Hosts: Fallow deer (Dama dama), roe deer (Capreolus capreolus)

Spiculopteragia spiculoptera

Synonym: Ostertagia spiculoptera, Spiculopteragia bohmi

Predilection site: Abomasum

Parasite class: Nematoda

Superfamily: Trichostrongyloidea

Hosts: Red deer (Cervus elaphus)

Apteragia quadrispiculata

Predilection site: Abomasum

Parasite class: Nematoda

Superfamily: Trichostrongyloidea

Hosts: Roe deer (Capreolus capreolus), red deer (Cervus elaphus), sika deer (Cervus nippon), fallow deer (Dama dama), moose (Alces alces), reindeer (Rangifer tarandus)

Rinadia mathevossiani

Predilection site: Abomasum

Parasite class: Nematoda

Superfamily: Trichostrongyloidea

Hosts: Red deer (Cervus elaphus), roe deer (Capreolus capreolus), sika deer (Cervus nippon), fallow deer

(Dama dama), moose (Alces alces), reindeer (Rangifer tarandus)

Ostertagia leptospicularis

Synonym: Skrjabinagia kolchida, Grosspiculagia podjapolskyi, Ostertagia crimensis

Predilection site: Abomasum

Parasite class: Nematoda

Superfamily: Trichostrongyloidea

Hosts: Fallow deer (Dama dama), roe deer (Capreolus capreolus), red deer (Cervus elaphus), sika deer (Cervus nippon), moose (Alces alces), reindeer (Rangifer tarandus), cattle, sheep, goat, camel

Notes: Considered to be a polymorphic species with two male morphs, Ostertagia leptospicularis and Skrjabinagia kolchida (Grosspiculagia podjapolskyi).

This species is described in more detail in Chapter

2 (Cattle).

SMALL INTESTINE

A number of intestinal species have been reported in deer (Table 8.2) but are generally of little clinical significance. The majority of these are parasites of cattle or sheep and are described in more detail under the chapters for these hosts.

A range of protozoa similar to those present in other ruminants is found in the intestine of deer. A number of Eimeria species have been reported in several species of deer but their significance is not known (Table 8.3).

Table 8.2 Intestinal helminths in deer.

PARASITES OF THE RESPIRATORY SYSTEM

Cephenemyia trompe

Common name: Reindeer throat bot

Predilection site: Nasopharynx

Parasite class: Insecta

Family: Oestridae

Description, gross: The adult is bee-like in appearance, 14–16 mm in length and covered in long, yellowish and black hairs overlying a shining black body. Developing larvae are white, while fully developed larvae are about 25–40 mm long and yellow-brown. The entire larval body is covered by bands of short spines on both sides and narrows posteriorly.

Hosts: Reindeer, deer, moose and caribou

Table 8.3 Eimeria spp of deer.

Life cycle: The adult flies are active from June to September and, like Oestrus, the females are viviparous. The fly hovers close to the animal, then darts in and ejects larvae in fluid into the nostrils of the host animal. The larvae migrate to the retropharyngeal pouches. There they become attached in clusters and develop. Further development occurs in the nasopharynx, as the larvae migrate to and crowd in the retropharangeal pouches that lie on either side of the throat at the base of the tongue. Fully developed, third-stage larvae, which may be 40 mm in length, crawl to the anterior nasal passages and are sneezed out. Pupation occurs on the ground under surface debris. The pupation period is about 4 weeks. The adult flies have no mouthparts for feeding so they are short-lived and mate shortly after emerging.

Geographical distribution: Throughout the northern holarctic region including Europe and North America

Pathogenesis: Although the larvae occasionally cause death from suffocation, their general effect is loss of condition. The adult flies cause disturbance and avoidance responses, which reduce feeding and result in loss of condition. In summer, keratitis and blindness may occur in reindeer if larvae are deposited in the eye.

Clinical signs: There are few external signs of the presence of deer nose bots, although there may be some nasal discharge. Occasionally, heavy infections may cause death by suffocation. Behaviour such as snorting and lowering or shaking of the head may indicate the migration of mature larvae within the nasal passages or oviposition activity of the adult fly.

Diagnosis: Occasionally a larva may be found on the ground after a severe sneezing attack, but often a positive diagnosis can only be made at necropsy.

Pathology: The retropharyngeal pouch may be enlarged and the epithelium of the pouch may be pitted or eroded and become partly detached, necrotic and oedematous in infected deer.

Epidemiology: C. trompe is considered to be a serious problem in domestic reindeer management in Scandinavia. It is estimated that in Sweden the losses due to C. trompe and the warble fly Oedemagena tarandi equate to approximately 15% of the income from reindeer production.

Treatment: Nose bots are generally well tolerated in wild hosts and treatment is not usually required.

Dictyocaulus viviparus

Predilection site: Bronchi, trachea

Parasite class: Nematoda

Superfamily: Trichostrongyloidea

Description, gross: The adults are slender thread-like worms; males measure around 4.0–5.5 cm and females 6–8 cm in length.

Description, microscopic: The buccal ring is triangular in shape. First-stage larvae are 300–360 μm with the intestinal cells containing numerous chromatin granules.

Hosts: Cattle, buffalo, deer (red deer) and camel

Geographical distribution: Worldwide, but especially important in temperate climates with a high rainfall

Table 8.4 Other species of bot flies (family: Oestridae).

Life cycle: The life cycle is as described under cattle. The prepatent period in red deer is 20–24 days and larvae are excreted for approximately 25 days.

Geographical distribution: Worldwide

Pathogenesis: Larval migration produces only a mild inflammatory response in the lungs. Thus, larger numbers of immature worms reach the pulmonary bronchi and heavy burdens of mature worms are well tolerated.

Clinical signs: In contrast with D. viviparus infection in cattle, coughing is not a common sign of affected red deer. Clinical signs commonly associated with lungworm infection are loss of condition, dull coat as well as inappetence, reduced weight gains, fever, increased tachycardia and tachypnoea, dyspnoea and death in severe cases.

Diagnosis: Presumptive diagnosis of infection can be made on clinical signs if young susceptible deer develop respiratory problems or inappetence. On postmortem examination, the diagnosis is confirmed by finding large numbers of lungworms and mucus in pulmonary airways and pneumonic changes in the lungs. Mature D. viviparus infection can be detected by recovery of first-stage larvae from faecal samples by the Baermann technique (see Chapter 15).

Pathology: Gross pathological changes in lungs are consolidation of the dorsal portion of the diaphragmatic lobes, excess mucus and lungworms in the trachea, bronchi and bronchioles, and enlarged bronchial lymph nodes. Death results from asphyxiation due to obstruction of the trachea and bronchi with adult lungworms and mucus.

Epidemiology: Clinical disease is more prevalent in autumn in deer calves kept under intensive conditions.

Treatment: Benzimidazole anthelmintics and macrocylic lactones are generally effective at increased dose rates.

Control: The importance and widespread occurrence of D. viviparus infection in farmed red deer has prompted a number of recommendations for its control. Clinical disease is exacerbated by stressors such as malnutrition and transport and often associated with high stocking densities. These conditions should be avoided as should grazing on pasture where cattle have grazed. Any introduced deer should be treated on arrival and then 3 and 6 weeks later. Live lungworm vaccine has been used as a preventative.

Dictyocaulus eckerti

Synonym: Dictyocaulus noerneri

Predilection site: Bronchi, trachea

Parasite class: Nematoda

Superfamily: Trichostrongyloidea

Hosts: Roe deer (Capreolus capreolus), fallow deer (Dama dama) and various other deer

Description, gross: Similar to D. viviparus

Description, microscopic: The buccal ring is kidneyshaped.

Geographical distribution: Worldwide, but especially important in temperate climates with high rainfall.

The following metastrongylid parasites have been reported in the lungs of various deer hosts. Control is impractical and rarely, if ever, indicated.

For more details of these species see Chapter 3 (Sheep and goats).

Protostrongylus rufescens

Common name: Small lungworm

Predilection site: Small bronchioles

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Definitive hosts: Sheep, goat, deer and wild small ruminants

Intermediate hosts: Snails (Helicella, Theba, Abida, Zebrina, Arianta)

Muellerius capillaris

Common name: Nodular lungworms

Predilection site: Lung

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Definitive hosts: Sheep, goat, deer and wild small ruminants

Intermediate hosts: Snails (Helix, Succinea) and slugs (Limax, Agriolimax, Arion)

Cystocaulus ocreatus

Common name: Small lungworm

Predilection site: Lung

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Definitive hosts: Sheep, goat, deer and wild small ruminants

Intermediate hosts: Snails (Helicella, Helix, Theba, Cepaea, Monacha)

Geographical distribution: Worldwide

Varestrongylus sagittatus

Synonym: Bicaulus sagittatus

Common name: Small lungworm

Predilection site: Lung

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Description: Adult worms are slender, small worms, 1.4–3.4 cm long.

Final hosts: Red deer (Cervus elaphus), fallow deer (Dama dama)

Intermediate hosts: Slugs and snails

Life cycle: Ingested third-stage larvae present within the intermediate host, migrate through the intestinal wall to the lymph nodes, migrating via the lymph and blood to the lungs. They then form ‘breeding clusters’ in which they grow to sexual maturity. Female worms are ovoviviparous with first-stage larvae coughed up and swallowed. When ingested by a molluscan intermediate host the larvae develop to infective L₃ in 3–4 weeks

Geographical distribution: Europe

Pathogenesis and clinical signs: Infection can cause pulmonary oedema, emphysema and inflammation of the lungs. Secondary bacterial infection can lead to pneumonia, emaciation and death.

Diagnosis: Varestrongylus first-stage larvae have a dorsal, posteriorly directed spine.

Treatment: Treatment with fenbendazole or mebendazole given over 3–5 days has been reported to be effective.

Varestrongylus capreoli

Synonym: Capreocaulus capreoli

Predilection site: Lung

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Final hosts: Roe deer (Capreolus capreolus)

All other details similar to V. sagittatus.

Echinococcus granulosus

See Parasites of the liver.

PARASITES OF THE LIVER

Fascioloides magna

Common name: Large American liver fluke

Predilection site: Liver and bile ducts

Parasite class: Trematoda

Family: Fasciolidae

Description, gross: Flukes are large and thick and measure up to 10 × 2.5 cm. The flukes are oval, with a rounded posterior end. They possess no anterior cone and when fresh are flesh-coloured (Fig. 8.1).

Description, microscopic: Eggs are large, operculate, measure 109–168 × 75–96 μm and have a protoplasmic appendage at the pole opposite the operculum.

Final hosts: Deer, cattle, sheep, goat, pig, horse

Intermediate hosts: A variety of freshwater snails, Fossaria spp, Lymnaea spp, Stagnicola spp

Life cycle: The life cycle is similar to that of F. hepatica. The eggs hatch to miracidia after 4 weeks or longer. Development in the snail takes 7–8 weeks. The prepatent period in deer is around 30 weeks.

Geographical distribution: Mainly occurs in North America, central, eastern and southwestern Europe, South Africa and Mexico

Pathogenesis: In deer (and cattle), the flukes are frequently encapsulated in thin-walled fibrous cysts in the liver parenchyma and this restricted migration results in low pathogenicity.

Fig. 8.1 Fascioloides magna.

Clinical signs: In deer and cattle the parasites can cause hepatic damage on reaching the liver but the flukes rapidly become encapsulated by the host reaction and clinical signs are minimal.

Diagnosis: This is based primarily on clinical signs. The presence of cysts and the large flukes are usually seen on postmortem examination. Faecal examination for the presence of fluke eggs is a useful aid to diagnosis.

Pathology: In deer, encapsulated thin-walled fibrous cysts are found in the liver parenchyma.

Epidemiology: The various snail intermediate hosts tend to occur in stagnant semi-permanent water that contains large amounts of dead or dying vegetation, swamp areas, or pools and streams. F. magna is indigenous to North America and is common in Canada and the Great Lake areas where the white-tailed deer and the elk are commonly infected.

Treatment: For cattle and sheep the commonly used flukicides such as triclabendazole, closantel, clorsulon and albendazole are effective. Mature F. magna are susceptible to oxyclosanide.

Control: Elimination of the snail intermediate hosts is difficult due to their varied habitats.

Notes: F. magna is primarily a parasite of deer (Cervidae) and is commonly found in white-tailed deer, elk and moose.

Fasciola hepatica

Common name: Liver fluke

Predilection site: Liver

Parasite class: Trematoda

Family: Fasciolidae

Definitive hosts: Sheep, cattle, goat, horse, deer, man and other mammals

Dicrocoelium dendriticum

Synonym: Dicrocoelium lanceolatum

Common name: Small lanceolate fluke

Predilection site: Liver

Parasite class: Trematoda

Family: Dicrocoeliidae

Final hosts: Sheep, goats, cattle, deer and rabbits, occasionally in the horse and pig

Intermediate hosts: Two are required. 1. Land snails of many genera, principally Cionella lubrica in N. America and Zebrina detrita in Europe. Some 29 other species have been reported to serve as first intermediate hosts of the genera Abida, Theba, Helicella and Xerophila. 2. Brown ants of the genus Formica, frequently F. fusca

Geographical distribution: Worldwide except for South Africa and Australia. In Europe the prevalence is high but in the British Isles prevalence is low, being confined to small foci throughout the country.

Dicrocoelium hospes

Predilection site: Liver

Parasite class: Trematoda

Family: Dicrocoeliidae

Hosts: Cattle and deer

Geographical distribution: Parts of Africa

Notes: Details are essentially similar to D. dendriticum

Stilesia hepatica

Predilection site: Bile ducts

Parasite class: Cestoda

Family: Thysanosomidae

Final hosts: Sheep, deer and other ruminants

Intermediate hosts: The intermediate host is probably an oribatid mite

Geographical distribution: Africa and Asia

Taenia hydatigena

Synonym: Taenia marginata, Cysticercus tenuicollis

Predilection site: Abdominal cavity, liver (intermediate hosts); small intestine (definitive hosts)

Parasite class: Cestoda

Family: Taeniidae

Final hosts: Dog, fox, weasel, stoat, polecat, wolf, hyena

Intermediate hosts: Sheep, cattle, deer, pig, horse

Echinococcus granulosus

Common name: Dwarf dog tapeworm, hydatidosis

Predilection site: Mainly liver and lungs (intermediate hosts); small intestine (definitive host)

Parasite class: Cestoda

Family: Taeniidae

Description: Hydatid cysts are large fluid-filled vesicles, 5–10 cm in diameter, with a thick concentrically laminated cuticle and an internal germinal layer.

Final hosts: Dog and many wild canids

Intermediate hosts: Domestic and wild ruminants, deer, man and primates, pig and lagomorphs; horses and donkeys are resistant

Geographical distribution: Worldwide

For more details of these species see Chapter 3 (Sheep and goats).

PARASITES OF THE CIRCULATORY SYSTEM

Babesia bovis

Synonym: Babesia argentina

Predilection site: Blood

Parasite class: Sporozoasida

Family: Babesiidae

Hosts: Cattle, buffalo, deer

Geographical distribution: Australia, Africa, Central and South America, Asia and southern Europe

For more details see Chapter 2 (Cattle).

Theileria cervi

Synonym: Theileria tarandi

Predilection site: Blood, lymph nodes

Parasite class: Sporozoasida

Family: Theileriidae

Hosts: Fallow deer, red deer, sika deer, white-tailed deer, reindeer

Notes: Little information is available on this species

Anaplasma marginale

Predilection site: Blood

Order: Rickettsiales

Family: Anaplasmataceae

Hosts: Cattle, sheep, goat, deer, camel, wild ruminants

Geographical distribution: Africa, southern Europe, Australia, South America, Asia, former Soviet States and USA

Anaplasma centrale

Predilection site: Blood

Order: Rickettsiales

Family: Anaplasmataceae

Hosts: Cattle, deer, wild ruminants, and perhaps sheep, may act as reservoirs of infection

Geographical distribution: Africa, southern Europe, Australia, South America, Asia, former Soviet States and USA

For more details of these species see Chapter 2 (Cattle).

PARASITES OF THE NERVOUS SYSTEM

Elaphostrongylus cervi

Synonym: Elaphostrongylus rangiferi

Predilection site: Connective tissue, CNS

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Description, gross: The mature worms are long and slender. Males are up to 40 mm long; and females up to 60 mm long.

Description, microscopic: First-stage larvae have a dorsal spine on the tail.

Final hosts: Red deer (Cervus elaphus), roe deer (Capreolus capreolus), sika deer (Cervus nippon)

Intermediate hosts: Various land and freshwater snails and slugs

Life cycle: Female worms lay eggs that either hatch in situ or are carried to the lungs via the boodstream and then hatch. Larvae migrate through the lungs to the airways and are then swallowed and pass out in the faeces. The larvae may survive in the environment for up to 2 years before infecting a molluscan intermediate host. The parasites develop through the second-stage larvae to the infective, third-stage larvae in the mollusc within 27–50 days and can retain their infectivity for up to another 2 years. Deer become infected when they ingest snails containing infective larvae. After ingestion, the larvae burrow through the gut wall and migrate to the final tissue site, at the same time developing into adult worms. The prepatent period is about 112 days.

Geographical distribution: E. cervi is present in most countries of northern and central Europe and the CIS States. It is also present in New Zealand.

Pathogenesis: The severity of clinical disease is very much influenced by the level of infection and location in the body. Light infections are usually subclinical. Three clinical syndromes are described:

• Acute disease characterised by hindlimb paralysis and perhaps blindness resulting from damage to the central nervous system.
  
• Chronic ill-thrift, resulting from connective tissue damage.
  
• Verminous pneumonia, resulting from larval migration.

Additionally, there may be economic losses through trimming, downgrading or condemnation of carcases.

Clinical signs: Most infections are inapparent. Clinical signs include exercise intolerance, hindlimb incoordination and nervous disorders.

Diagnosis: Diagnosis is based on finding the infective larvae in faeces using the Baermann method. The first-stage larvae have a characteristic dorsal spine on their tails and look very like the protostrongylid larvae of Muellerius spp that infest sheep.

Pathology: Connective tissue lesions are most likely to be found in the muscles of the neck, shoulders, flanks and loins. These consist of green discoloration of fascial sheets, and chronic granulomata with encapsulated, degenerated worms. Similar lesions may he seen in regional lymph nodes. Worms associated with central nervous system lesions are most likely to be seen in the subdural and subarachnoid spaces. Pulmonary lesions consist of a diffuse interstitial pneumonia with focal emphysema and consolidation.

Epidemiology: This parasite affects a number of deer species and the prevalence of infection is generally high in both wild and farmed deer.

Treatment and control: Fenbendazole given on 3 consecutive days has been reported to be effective. Control is difficult given the ubiquitous nature of the intermediate hosts.

Notes: The nomenclature of this parasite remains controversial.

Parelaphostrongylus tenuis

Synonym: Odocoileostrongylus tenuis, Elaphostrongylus tenuis

Common names: Cerebrospinal nematodiosis, meningeal worm, moose sickness, moose disease

Predilection site: Veins and venous sinuses of cranial meninges, CNS

Parasite class: Nematoda

Superfamily: Metastrongyloidea

Description, gross: The mature worms are long and thread-like; males are up to 40 mm and females up to about 90 mm.

Description, microscopic: First-stage larvae have a dorsal spine on the tail.

Final hosts: White-tailed deer (Odocoileus virginianus), moose (Alces alces), wapiti (Cervus canadensis), other deer species, llama, guanaco, alpaca

Intermediate hosts: Snails and slugs

Life cycle: Unembryonated eggs are released into the bloodstream and travel to the lungs where they lodge in the capillaries and complete their development to L₁ before moving to the alveoli from where they are coughed up and swallowed and passed in the faeces. To develop further they must penetrate or be eaten by a slug or snail. In the foot of the snail the larvae develop through the second-stage larvae to the infective, third-stage larvae. Deer become infected when they accidentally ingest slugs or snails containing infective larvae. After ingestion, the larvae burrow through the gut wall and migrate to the CNS via the spinal nerves and spinal cord, at the same time developing into adult worms. The prepatent period is about 82–137 days.

Pathogenesis: In the white-tailed deer the parasite causes little clinical effect but in other cervids and camelids can cause debilitating neurological signs and in North America is the causative agent of ‘moose sickness’. Llamas and their relatives are susceptible to P. tenuis.

Clinical signs: Signs of infection are rare in whitetailed deer. Infected moose may show swaying, paraparesis, torticollis, circling, blindness, ataxia, paresis, difficulty in standing, weight loss and death. In red deer (wapiti), there is progressive neurological disease and death.

Diagnosis: Diagnosis is based on finding adult worms in the CNS.

Epidemiology: P. tenuis is a common parasite of white-tailed deer in North America. Infection occurs in moose that share the same range as white-tailed deer.

Treatment and control: Not practical. Strict management of national and international deer translocations should be practised wherever possible.

PARASITES OF THE REPRODUCTIVE/UROGENITAL SYSTEM

No parasites of veterinary significance reported.

PARASITES OF THE LOCOMOTORY SYSTEM

Taenia cervi

Synonym: Cysticercus cervi, Taenia krabbei, Cysticercus tarandi

Predilection site: Small intestine (definitive host); muscle (intermediate host)

Parasite class: Cestoda

Family: Taeniidae

Final hosts: Wolf, red fox, artic fox

Intermediate hosts: Red deer (Cervus elaphus), roe deer (Capreolus capreolus), reindeer (Rangifer tarandus)

Life cycle: Wild canids are infested by consuming the cysticercus in the intermediate host. The intermediate host is infected through the ingestion of tapeworm eggs that hatch in the intestine.

Geographical distribution: Worldwide

Pathogenesis: Cysticerci may cause economic loss through condemnation at meat inspection.

Clinical signs: Adult tapeworms are considered to be of little pathogenic importance. Infected intermediate hosts do not usually show clinical signs of disease.

Diagnosis: Diagnosis is through the identification of cysts at postmortem.

Pathology: The mature, ovoid white cysticerci are grossly visible in the muscle, heart, lung, liver and brain.

Epidemiology: Deer are infected by grazing pasture and forages contaminated with carnivore faeces harbouring taenid eggs.

Treatment and control: Control is not practical.

Notes: The correct nomenclature for the intermediate host stage is the ‘metacestode stage of Taenia cervi’ rather than ‘Cysticercus cervi’. It is unclear whether Taenia krabbei found mainly in reindeer is synonymous with T. cervi, which is found mainly in red deer and roe deer, and that they are one and the same species present in different hosts.

Several species of Sarcocystis have been reported in deer (Table 8.5). Specific details are beyond the scope of this book.

PARASITES OF THE CONNECTIVE TISSUE

Elaeophora schneideri

Common name: Filarial dermatosis, ‘sore head’

Predilection site: Blood vessels

Parasite class: Nematoda

Superfamily: Filarioidea

Definitive hosts: Sheep, goat, deer (elk, moose, mule deer)

For more details see Chapter 3 (Sheep and goats).

Hypoderma diana

Common name: Warble fly

Predilection site: Subcutaneous skin

Parasite class: Insecta

Family: Oestridae

Description, adults: Adult female Hypoderma diana are about 15 mm in length and bee-like in appearance; the abdomen is covered with yellow–orange hairs with a broad band of black hairs around the middle. The adults have no functioning mouthparts.

Description, larvae: The mature larvae are thick and somewhat barrel-shaped, tapering anteriorly. When mature they are 25–30 mm in length and most segments bear short spines. Larvae are dirty white in colour when newly emerged from the host, but rapidly turn dark brown. The pupa is almost black. The larvae are relatively host specific and live as subcutaneous parasites of deer.

Hosts: Deer

Life cycle: Females emerge with all their eggs fully developed. They have a relatively short lifespan in which they do not feed, and are able to mate and oviposit soon after emergence. Mating takes place off the host at aggregation points where females are intercepted in flight. The female lays between 300–600 eggs on the lower regions of the legs and lower body of the host animal, where they are glued to the hairs.

The first-stage larvae are less than 1 mm in length, hatch within a week and crawl down the hairs, either burrowing directly into the skin or into the hair follicles. The larvae then continue to burrow beneath the skin. Hypoderma diana migrates below the skin along nerves to the spinal cord. After about 4 months, usually by autumn, larvae reach the epidural fat of the spine in the region of the thoracic and lumbar vertebrae, where they overwinter. Next spring, migration is resumed until, about 9 months after oviposition, the larvae reach the skin of the back. A characteristic small swelling (the ‘warble’) is formed and a small hole is cut to the surface. A cystic nodule then begins to form around each larva. The larva reverses its position and rests with its two posterior spiracles close to the opening in the warble, allowing the larva to breathe. In this location the larva moults twice, during which time it grows rapidly, more than doubling in length. Larval migration and growth take place in the host until April. The larvae then drop off the host animal and pupate in soil. The fly emerges after approximately 36 days. The duration of pupation depends on ambient temperature and ground cover; higher pupal survival occurs when there is at least some grass cover and where the ground does not freeze.

Table 8.5 Sarcocystis species found in deer.

Geographical distribution: Northern hemisphere

Pathogenesis: The fly is most active in May and June, but it is not recognised as a cause of ‘gadding’ in deer. The mature larvae occur subcutaneously along the back, and hide damage occurs with linear perforations.

Clinical signs: Except for poor growth in severe cases, the hosts show no symptoms until the larvae appear along the back, when the swellings can be seen and felt. The larval migration is not usually noticed clinically, but heavy infestations may reduce growth. Occasionally the pressure of larvae on the spinal cord can cause paralysis. When the larvae reach the skin on the animal’s back, large, soft, painful swellings of up to 3 mm diameter develop. The larvae lie in cysts containing yellow purulent fluid.

Diagnosis: The presence of the larvae under the skin of the back of deer allows diagnosis of warble flies. The eggs may also be found on the hairs of the animals in the summer.

Pathology: Warble larvae induce a pronounced tissue inflammation. The cellular reacton is predominantly eosinophilic and lymphocytic. The presence of the larvae also induces the production of a thickened connective-tissue lined cavity, surrounding the larva, filled with with inflammatory cells, particularly eosinophils.

Epidemiology: Hypoderma diana is present in a great variety of habitats, overlapping the territory of its hosts. It is spread throughout Europe and Asia, from 30° to 60° north, living in several different ecological zones, such as mixed, deciduous and coniferous forests, wooded steppes and wetlands. The adult fly is most active in May and June, particularly on warm, sunny days. The main factors influencing the flight and oviposition of female flies are ambient air temperature and light, as a result of which they are most active at midday. As in other species, the extent of parasitism and prevalence are higher in younger animals, possibly due to a measure of resistance in adults built up through repeated contact with the parasite. The degree of parasitism in male deer is usually higher than in females and castrated animals.

Treatment: Like other species, Hypoderma diana is highly susceptible to systemically active organophosphorus insecticides and to the macrocyclic lactones ivermectin, doramectin, eprinomectin and moxidectin.

Control: For farm-raised deer a control programme may be implemented, with regular treatment timed in relation to the local population dynamics of Hypoderma. Animals may be given some protection by being herded into corrals, shelters or shaded areas to reduce the risk of infestation when adult flies are active.

It is more difficult to develop effective control measures for diseases in wild and semi-wild deer. Here it is important that any attempted parasite controls do not have an effect on the environment in which the animals live. For free-range deer that cannot be captured, food may be supplemented with oral forms of antiparasitic preparations. However, care must be taken in selecting a suitable food medium for the antiparasitic agent, since it cannot be freely distributed around the environment because it may be eaten by other animals; neither can the volume ingested be controlled.

Notes: With the success of control measures against warbles in cattle it is important to realise that H. diana, although capable of infecting many species of deer, will not infect cattle. As a consequence of this, even in areas where (as is commonly the case) almost all the deer carry the parasitic larvae, cattle are not at risk.

Hypoderma tarandi

Synonym: Oedemagena tarandi

Common name: Reindeer warble

Predilection site: Subcutaneous connective tissue

Parasite class: Insecta

Family: Oestridae

Description: Large, hairy flies with reddish yellow hairy abdomens. Mature, third-stage larvae are approximately 25 mm in length.

Hosts: Reindeer, musk ox and caribou

Life cycle: The life cycle of Hypoderma tarandi resembles that of other species in the genus Hypoderma. They are active in July and August, each female laying between 500 and 700 eggs, which are attached to the downy undercoat rather than the outer hair. The flanks, legs, and rump are preferential laying sites. After approximately 6 days the egg hatches on the skin, and the larva then burrows into and under the skin. Unlike other Hypoderma, however, the L₁ migrates directly to the back in the subcutaneous connective tissue via the spine. When the larva comes to rest in about September to October, a swelling (warble) is created around it where it feeds on the animal’s blood and body fluids. The L₃ makes a cutaneous perforation and the larvae breathe by applying their spiracles to the aperture. When growth is completed in the spring, the larva leaves the reindeer through its air hole and drops to the ground to pupate. It then emerges as an adult fly, completing the cycle.

Geographical distribution: Circum-arctic and subarctic regions of Europe, Asiatic Russia and America

Pathogenesis: The adult flies cause gadding, and the newly hatched larvae may cause dermatitis with local oedema when they penetrate the skin. The main importance of this genus, however, is economic, from damage to hides by the L₃. In Sweden this loss can amount to a fifth of the total income from reindeer herds. Up to two hundred holes may be found in typically infested reindeer skins in Russia.

Clinical signs: Except for poor growth in severe cases, the hosts show no symptoms until the larvae appear along the back, when the swellings can be seen and felt. The larval migration is not usually noticed clinically, but heavy infestations may reduce growth. Occasionally the pressure of larvae on the spinal cord can cause paralysis. When the larvae reach the skin on the animal’s back, large, soft, painful swellings may be observed. The larvae lie in cysts containing yellow purulent fluid. Attacks by warble flies laying eggs can cause irritation to reindeer. Host animals may injure themselves as a result.

Diagnosis: The presence of the larvae under the skin of the back allows diagnosis of warble flies. The eggs may also be found on the hairs of the animals in the summer.

Pathology: Warble larvae induce a pronounced tissue inflammation. The cellular reacton is predominantly eosinophilic and lymphocytic. The presence of the larvae also induces the production of a thickened connective tissue lined cavity surrounding the larva, filled with with inflammatory cells, particularly eosinophils.

Epidemiology: Fawns and yearlings are most affected by this parasite, which produces large oedematous swellings. These swellings may suppurate and attract blowflies, which then oviposit in the wound.

Treatment: Injectable ivermectin, doramectin, eprinomectin or moxidectin administered between November and January is extremely effective in eliminating these parasites.

Control: In control schemes a single annual treatment in autumn is usually recommended before the larvae have reached the back and perforated the hide.

Notes: Limited geographical distribution but of local veterinary importance

PARASITES OF THE INTEGUMENT

Besnoitia tarandi

Predilection site: Skin, conjunctiva

Order: Sporozoasida

Family: Sarcocystiidae

Intermediate hosts: Reindeer, caribou

Final host: Unknown

ECTOPARASITES

LICE

Lice infestations are frequently encountered in deer. It is beyond the scope of this book to provide detailed descriptions of all the species of lice that may be encountered on deer throughout the world. Some of the more common species that may be encountered are provided in Table 8.6.

Treatments with insecticides, such as carbaryl, cypermethrin, deltamethrin, diazinon, lindane, and malathion, are usually effective in controlling lice on deer. Insecticidal dust bags or ‘back rubbers’ can be used as self-dosing rubbing stations for deer, and other ungulates. Because louse populations on most temperate ungulates increase during the cooler months, insecticides should ideally be administered to them in the autumn/winter months. Avermectins are generally less effective against chewing lice but may be effective against sucking lice. Animals destined to be introduced into established herds should be quarantined and where necessary treated.

MITES

Sarcoptes scabiei

Predilection site: Skin

Parasite class: Arachnida

Sub-class: Acari

Order: Acariformes

Sub-order: Sarcoptiformes (Astigmata)

Family: Sarcoptidae

Hosts: Red deer, roe deer, moose, reindeer

For more details see Chapter 5 (Pigs).

Table 8.6 Lice on deer.

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