Parisitology

Question 1

Define a PARASITE

Answer 1

A parasite is an organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other’s expense. The host is not killed.

Question 2

What are the types of parasitic host?

Answer 2

• intermediate host - host in which asexual growth and development occur
• definitive host - host in which sexual reproduction and development occurs

Question 3

Define SYMBIOSIS

Answer 3

Symbiosis is the association between the parasite and its host; it is an association between two different organisms living in close physical association. Each party in the relationship is called a symbiont.

Question 4

What are the types of parasites?

Answer 4

1. Endoparasites - live internal to the host

2. Ectoparasites - live external to the host

Question 5

What are the different parasitic ranges?

Answer 5

1. Temporary - the parasite is only on the host to feed, or only off the host to disperse
2. Permanent - once the parasite enters the host it remains there until it dies
3. Obligate - the parasite needs to spend at least part of its life cycle living off its host
4. Facultative - the parasite can survive without its host

Question 6

What are ectoparasites?

Answer 6

These live outside the host’s body, spending only a short time on their host (often only a blood meal). They are micropredators and feed off of several individuals

Question 7

What are some different types of ectoparasites?

Answer 7

Flies, midges and lice

Question 8

What types of parasitosis is caused by flies?

Answer 8

• nuisance - e.g. musca domestica - house fly
• biting stress - e.g. stomoxia calcitrans - stable fly
• mylasis - e.g. lucilia sericata - blow fly, oestrus ovis - sheep bot fly, gasterophilus spp - bot fly, dermatobia hominis - warble fly

Question 9

Describe a stable fly

Answer 9

Has a life cycle of 28 days on average.
1cm long
Has a biting mouthpiece to obtain blood
Are a vector for several protozoal and helminthe diseases of animals
Maggots develop in decaying feed and manure

Pathology: bite - pain - annoyance

Question 10

Describe a bot fly

Answer 10

1.5cm long
Adults are robust, dark, and long with a protuberant abdomen
Larvae have spined segments and posterior spiracles and are red/orange in colour

Life cycle: Adults lay eggs on hairs, eggs are taken to mouth by licking when grooming, penetrates tongue/mouth mucosa, emerge from the tongue and are swallowed, attach to epithelium in stomach and feed on blood. Detach in the summer and passed out through faeces.
Pathology: lesions in the mouth and on the tongue, ulceration in the stomach

Question 11

What are some types of biting fly?

Answer 11

Midges, moquito, black flies, warble flies

Question 12

What are lice?

Answer 12

They are host specific. They spend their whole life cycle on the host and have 3 larval stages.
Symptoms: irritation, severe itching, hair loss, skin abrasions.

Question 13

What are some different types of lice?

Answer 13

1. Haematopinus asini - horse sucking louse
   Lay eggs in hair follicles, causes heavy dandruff, greasy skin and bald spots. May also cause anaemia and weight loss
2. Bovicola Damalinia Equi - biting louse
   Feeds on hair scales and skin debris, causes intense irritation, is a vector for equine infectious anemia. Spreads via direct contact

Question 14

What are endoparasites?

Answer 14

These are parasites that live inside the host.

Question 15

What are some examples of endoparasites?

Answer 15

Roundworms, tapeworms, bots

Question 16

What are strongylida?

Answer 16

These are red worms, they may be large or small. They are reddish brown in colour and are found in the cecum and in the colon.
Large strongyles are now uncommon due to the use of modern wormers, however small strongyles are the most prevalent.

Question 17

What is the lifecycle of large strongylida?

Answer 17

• adults in the caecum and colon. The eggs are passed to the outside through the horse’s faeces.
• hatching and larval development will occur in summer temperatures (8-38 degrees)
• infection is by ingestion of the larvae

Question 18

Describe small strongylida

Answer 18

The most common intestinal worm to affect horses. Adult worms live in the caecum and colon, in the gut wall. Larvae burrow into the gut wall and become encysted. Either they will emerge from the gut wall in a few weeks and become adults or they enter a period of hibernation and remain in the gut wall. They will then emerge at some point, giving way to clinical symptoms such as diarrhoea, rapid weight loss, colic and death.

Question 19

What are ascaridia?

Answer 19

A type of round worm found mainly in foals (horses develop immunity by around 18 months).
Larvae penetrate the wall of the small intestine. They subsequently migrate to the liver and the lungs where they are coughed up, reswallowed and return to the small intestine the develop into adults and lay eggs.

Question 20

What are oxyurida?

Answer 20

Have long, sharp pointed tails. Cause external pruritus, and in extreme cases gastrointestinal inflammation.

Question 21

What are some other nematodes?

Answer 21

Threadworms, lungworm, flatworms, tapeworms, dwarf tapeworms

Question 22

Define MYLASIS

Answer 22

Mylasis is the parasitic infestation of the body of a live animal by fly larvae that grow inside the host whilst feeding on its tissue.

Question 23

How can stable flies be controlled?

Answer 23

Remove moist bedding and food waste from stables, spray aerosol insecticide

Question 24

How can bot flies be controlled?

Answer 24

Wash the coat of the horse with a sponge containing insecticides if eggs are detected.

Question 25

What are some different types of mites?

Answer 25

1. Psoropres equi - scab mite. Causes ear infections, mane and tail irritation.
2. Chorioptes equi - chorioptic mite - infects the skin of the legs and causes inflammation and irritation
3. Sarcoptes scabiei var equi - burrowing mites. The female burrows into the skin to lay eggs. Transmission occurs through contact and treatment is prescribed by a vet.

Question 26

What are the different types of roundworms?

Answer 26

Small strongyles, large strongyles, ascarids, pinworms, intestinal threadworms,