Lecture 3 - Pig ectoparasites

Mites

Lice

Sarcoptes scabiei var suis

Haematopinus suis

Sarcoptes scabiei var suis

Sarcoptic mange

most important ectoparasite of the pigs;

In several states of Australia, sarcoptic mange in pigs is a

notifiable disease.

Sarcoptes scabiei var suis

Significance for human health

S. scabiei var suis can temporarily infest humans (Pig handler's itch);

The parasite does not seem to reproduce/complete its life cycle on humans -> clinical signs disappear in 2-3 weeks;

Constant exposure (pig handlers) -> clinical signs last longer;

Sarcoptes scabiei: Life cycle

Egg, larva, two nymphal stages and adults -> takes 2-3 weeks to complete

The fecundated females burrow tunnels in the skin and lay eggs in the tunnels;

Sarcoptes scabiei var suis - MORPHOLOGY

• Shape of the body: oval/circular, ventral surface is

flattened while the dorsal surface is convex;

• Gnathosoma: almost square;• On the dorsal side of idiosoma there are:

Transversal striations

Spines

triangular scales

The legs are short and conical:

Sarcoptes scabiei var suis

SOURCES OF INF.

Sources of infection (infestation)

• Animals with chronic/hyperkeratotic lesions (ear, forehead, legs), especially adult breeding animals: sows and boars

Sarcoptes scabiei var suis

TRANSMISSION

Piglets become infected (infested) from the sow during suckling;

Group housing of sows favors the spread of the mites between the adult females;

Sorting pigs by size at weaning favors the spread of parasites between litters.

Sarcoptes scabiei var suis

Epidemiology

Animals become infested mainly by direct contact

Pigs huddle, grouping the pigs etc favor transmission;

Transmission from one herd to another: when pigs with unapparent infestations are moved/introduced to new farms;

Highly contagious disease -> usually many animals will become infested in short time;

Prevalence and severity seem to increase in cooler months and decrease in warmer months.

Sarcoptes scabiei var suis

Pathogenesis

• Burrowing mites cause irritation

Delayed and immediate hypersensitivy develop to parasite secretions, faeces and eggs;

Hypersensitivity develops 3-4 weeks after infestation -> congestion of the skin, papules, pruritus;

Hyporeactive animals develop thick crusts that contain large number of parasites;

Within a group of pigs there seems to be two populations of pigs:

- A larger population of pigs harbour few mites and develop a marked hypersensitivity reaction

- A smaller population of pigs that harbour significant numbers of mites but do not develop a severe form of hypersensitivity;

Sarcoptes scabiei var suis

Clinical signs

Two main clinical forms:

I. Allergic/hypersensitive form

• Growing pigs

II. Hyperkeratotic/chronic form

• Old animals

I. Allergic/hypersensitive form

Seen often in young growing pigs;

Incubation period: 1-2 weeks;

• Pruritis

- Scratching/rubbing against the walls/fences & head shaking  hyperkeratosis, alopecia, thickening of the skin

Congestion of the skin, papules excoriations

Nodules, crusts;

Yellow-brown crusts in the ear, ear shaking

Sarcoptes scabiei var suis

I. Allergic/hypersensitive form

Sarcoptes scabiei var suis

Clinical signs

Lesions of hyperkeratotic mange develop in only few animals, those that fail to develop the hypersensitivty reactions -> in the ears thick crusts, hind legs etc;

Clinical signs might regress after 2-3 months;

II.Hyperkeratotic/chronic form

• Seen commonly in adult or in debilitated animals:

• Thick crusts (asbestos type) in the ears, on the head, forehead, neck, legs, tail etc;

• The skin is thickened and wrinkled;

• Pruritus is reduced

• Most sows and boars might have lesions (crusts) only on the inner surface of the ears without other obvious clinical signs -> source of infestation!!

Sarcoptes scabiei var suis

II. Hyperkeratotic/chronic form

Thick crusts (asbestos type) in the ears, head, forehead, neck, legs, tail etc

Sarcoptes scabiei var suis Diagnosis

1) Clinical signs

Congestion, pruritus, papules, pruritus,scratching etc;

2) History

• Age (growing pigs), time of the year, management, treatments etc;

3) Microscopic examination

May be of value in the chronic form of the disease:

a) Skin scrapings: papules rarely harbour parasites

b) Examination of crusts from ears

Pigs with hypersenstive form: not all infested pigs have positive ear scrapings

Pigs with hyperkeratotic form: ear scrapings are positive and the number of parasites is likely to be high

4) Serology

Differential diagnosis

• Parakeratosis, exudative epidermitis, deficiencies in niacin and biotin, swine pox, dermatomycosis etc

Sarcoptes scabiei var suis: Diagnosis

Sarcoptes scabiei var suis: Diagnosis 2 HISTO

Sarcoptes scabiei var suis

Treatment

Formamidines

- Amitraz: Taktic

• Spray: 2 treatments at 7-10 days interval of time

• The thick crusts that contain large numbers of mites might be difficult to penetrate!

• Pour on

Macrocyclic lactones

Ivermectin: SC injection twice at 14 day intervals or in food for 7

consecutive days;

Doramectin: SC/IM one injection;

Sarcoptes scabiei var suis Control

Target the breeding animals: they are the source of infestation;

Aim to prevent infestation of the piglets from the sow;

- ‘All in all out’

- Boars: treat regularly (every 2 to 3 months) because of

their constant contact with sows;

- Sows/gilts: treat 7-14 days prior to farrowing

- Piglets: treat at weaning and during the growing period as required

- Purchase pigs from free farms and check them very carefully during the period of isolation;

- Treat all animals introduced into the herd;

Elimination (eradication): possible (most programmes use Ivermectin or Doramectin);

Haematopinus suis

Head is narrower than the thorax;

Obvious angular process (ocular points) behind the antennae;

- Paratergal plates

Three pairs of legs that have the same size.

Feed on blood;

Haematopinus suis: Life cycle

• Spends its entire life cycle on the host;

• Eggs are cemented on the hair of the host

- Three nympshal stages, last one molts to adults

Life cycle might take 23-30 days;

Lifespan: 35-40 days;

Haematopinus suis

Epidemiology

- Lice are host specific -> commonly introduced to a herd with purchased infested stock;

- Boars and sows are sources of infestation

- Transmission: usually by direct contact

- Larger populations can develop on young animals and

animals with deficient diets & management

- Populations of lice are generally larger during the cold season

Haematopinus suis

Clinical signs

Feed on blood (all stages) -> anemia & reduced growth rate in young pigs;

H. suis may cause irritation -> pruritus, -> scratch -> loss of hair, crusts, excoriation, anorexia, and decreased weight gains.

Haematopinus suis

Diagnosis

• Clinical signs: scratching & rubbing, alopecia, anaemia in

young pigs;

• Visualization of lice on the body and eggs attached to the hairs of the pigs;

Haematopinus suis

Treatment

• Formamidines - Amitraz

• Macrocyclic lactones - Ivermectin, doramectin

Haematopinus suis

Control

Treat all the breeding and feeding stock to break the lifecycle;

Treat the sows before farrowing;

Treat the newly bought stock before

introduction to the herd;