yr4review of the common internal parasites of swine

7/30/2019 Yr4Review of the Common Internal Parasites of Swine

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Review of the Common InternalParasites of Swine


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Introduction:

Most parasitic infections of swine will be diagnosed by

finding the adult or larval parasites or the lesions

they produce while performing a necropsy. However, in

reviewing the common spp. Of swine parasites, a

characteristic egg has also been included. If a more

thorough explanation of the Salient Points, or

Feature of the Life Cycle is necessary, please see

your corresponding lecture notes from the second year or

appropriate texts.


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Unembryonated egg ofAscaris suum:

(50-75 um x 40-50 um) -eggs are

unembryonated in fresh feces, oval,

brownish and possess an irregular

albuminous coat. Occasionallyunfertilized eggs are passed which

vary in shape and lack the irregular

coat.


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Embryonated eggs ofAscaris suum:

When allowed to stand for a timeat room temperature, eggs may

contain larvae.


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Life Cycle features ofAscaris suum:

The infective stage (L2) occurs in the

eggs which hatch upon ingestion. Tissue

migrations follow the hepaticotracheal

route and may be completed as early as

10 days. Resulting L4 larvae molt and

mature to egg producing adults in 43-50

days. Most worms are expelled by 23rdweek of patency.


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AdultAscaris suum: heavy infection

Large numbers of adult worms adult

may occlude or perforate the gut.Migration into the bile duct has been

reported. This migration may occur

after treatment.


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Gross liver lesions

These are produced by host response

to migrating larvae and maycauseconsiderable loss at slaughter due

to condemnations. The majority of

these may resolve in a period of

25- 40 days. Some heavy infectionsmay be found in the intestines

without any visible liver damage.:


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Lungs of an 11-week-old pig:

with chronic pneumonia and heavy ascarid

infection. Thumps or a soft moist cough

which occurs early (7 10 days) after

ascarid has been attributed to migrating

larvae. This point has been questioned by

some authors.


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Oesophagostomum spp. Egg(73 89u x 34

45u)

These eggs are typical thin-

shelled strongyle-type eggs and are

similar to the eggs of the red stomach

Hyostrongylus.


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Oesophagostomumnodules in large

intestine. These worms are very

common in older swine, infection

occurs by ingestion of third stage

larvae which encyst in nodules

later to emerge as L4. The

prepatent period is 23 - 53 days

according to species.


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Oesophagostomum: salient points:

The nodular worm of swine are

generally considered non-pathogenic

although very heavy infections may

cause G.I. disturbances.Rx:piperazine

salt, TBZ. levamisole. fenbendazole,

ivermectin. Dechlorvos, and pyrantel.


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Strongyloides ransomi: eggs (45-55 u. x

26-35 um) eggs are similar to other

Strongyloides sp. , thin-walled and

larvated.


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Life cycle features ofStrongyloides ransomi:

Three routes of infection occur, prenatal,transcolostral and percutaneous( lung migration).

Prepatent periods are very short ( 210 days)


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Section of pig intestine showing location

and small size of adult worms.


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Comparison of litter mate pigs:

Heavy infections ofStrongyloides, may be fatal or

severly affect growth


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Strongyloides: salient points

The earliest parasitic infection producing signsin very young animals. RxTBS, levamisole.


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Trichuris suis egg: ( 5060u x 2125 u)

Trichuroid egg with mucoid plugs. These are

common worms of swine


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Trichuris suis adults: in pig cecum

Like all whipworms the thin anterior end is

embedded in the mucosa. Heavy infections have been

reported to cause necrosis, edema, hemorrhage, ulcerlike

lesions and nodule formation in the cecum and colon, but

these are generally considered to be rare.


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Trichuris suis: salient points

Characteristics are similar to those of other

whipworms, direct life cycle. Rxdichlorvos,

fenbendazole.


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Stomach worms

Three species of stomach worms commonly

occur in swine:

a.Hyostrongylus rubidus: red stomach

worm ( a trichostrongyle)

b. Ascarops strongylina: thick stomach

worm ( a spirurid)

c. Physocephalus sexalatus: thick

stomach worm ( a spirurid


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Hyostrongylus rubidus: eggs

Diagnosis of this infection by finding eggs in

the feces is difficult since they are similar to

Oesophagostomum eggs. Cultures can be made and 3rd

stage larva identified. Pathology varies from hyperemia to

eroded areas of ulcers. The occurrence of clinical disease

due to these infections is questionable


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Physocephalus eggs:

Thick-walled, larvated, spiruroid type

eggs. ( 2226u x 4145 u)Ascarops eggs maybe slightly smaller (3439u x 1517 u) but are

difficult to distinguish fromPhysocephalus


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Thick stomach worms: in mucosa of stomach

Pathology rare, may cause gastritis with

pseudomembrane formation


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Swine stomach worms: salient points

Life cycle are of trichostrongyle and

spiruroid types, worms are common in pastured

swine. RxHyostrongylus(TBZ, levamisole,

dichlorvos); spiruroids (dichlorovos).


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Gongylonema egg( 5070u x 2537 u)

Thick-walled, larvated egg, spiruroid type

egg, larger than stomach worm eggs.


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Gongylonema adult in tongue of pig

Non-pathogenic, life cycle of spiruroid

type, may also occur in mucosa of the

esophagus.


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Metastrongylus spp. Egg( 4557u x 3841u)

Three species of lungworms

commonly occur in pastured pigs, in the S.E.

all produce thick-walled, larvated eggs

similar in size toAscaris eggs.


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Metastrongylus adults in pig bronchi:

A moderate amount of tissue change( and

respiratory distress) have been directly associated

with the worms. Worms act as vectors of swine

influenza and possibly other viruses.


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Metastrongylus: salient points

Transmission is via ingestion of infected earthworms.

Rx- Levamisole, fenbendazole, ivermectin.


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Stephanurus dentatus eggs ( 100u x 60u)

Rarely if ever used in diagnosis, they are found in

urine


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Stephanurus adults in urethral cyst


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Stephanurus liver damage

The predominant ( necrotic abscesses and fibrosis)

produced occur in the liver during larval migrations.Other tissues may also be involved.


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Stephanurus salient points

The major problem associated with S.

dentatus infections is condemnation at slaughter. Rx -

Fenbendazole, ivermectin, levamisole(adults only)


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Macrocanthorynchus hirudinaceus eggs (67110u x 40

65u)

Thick-shelled, dark brown, football-shaped


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M. Hirudinaceus nodules on serosal

surface of pig small intestines.

They are due to the proboscis attachment.Generally non-pathogenic, may perforate

gut


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M. Hirudinaceus adults attached to small intestines

They can be differentiated from ascarids by presence ofproboscis, and wrinkled sometimes flat appearance


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Balantidium coli cysts

Common in swine rarely pathogenic, 4060u

organism can be recognized in cyst.


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Balantidium coli on occasion will invade mucosa, causing

ulceration and enteritis of large intestine. Tetracyclines are

effective.


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kkkk The Endkkkk

yr4review of the common internal parasites of swine

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