Parasitic Diseases important in Meat Inspection

ByDr. NYAKARAHUKA LUKE(BVM, MPH CANDIDATE)

TRICHINELOSIS

• Etiology– Trichinella spiralis, T. nativa, and T. britovi

• Hosts– All mammals, principally, pigs, man, rats, etc

• Life cycle. Clean life cycle. It has no free living stages outside the host.

• After ingestion, it gets encysted in the muscles• Larvae get released from muscles by action of

digestive enzymes.• Larvae enters the lymphatic system to the

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It is common in developing countries where meat fed to pigs is raw or undercooked

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Trichinellosis

• Predilection site is Muscles• Host reaction can lead to calcification • Caused by eating raw or undercooked pork or

wild game infected with the larvae• Diagnosis

– Trichinoscopy tests .Taking a piece of muscle esp diaphragm and compress it between two glass slabs and view on microscope

– Artificial Digestion using gastric juices– Serological tests

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Parasite Control Measures

• Through cooking of meat of meat at a temp not less than 60oc

• Freeze at -150c for at least 30 days• Avoid feeding swill or garbage to pigs• Drying is ineffective, but salting and smoking

can be effective

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Judgment for Trichenollosis

• Total condemnation of the entire carcass

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Taeniasis(Cestodes)

• Segmented worms that live in intestines• Adults release last maturing

segments(Progrolitids) can be gravid with over 30,000.

• These are passed into feces and hatched into larvae on the ground .

• Larvae are ingested by animals, migrate to their predilection sites to form cystic forms

• These cystic forms are the ones infective to man.

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Taeniasis

• 3 types of cyst occur– cysticercus. Has got an outer membrane enclosing

a single scolex, each with a varying degree of fluid.– Coenurus(Multiceps cysts), with single cyst and

several scoleces– Hydatid cysts(Echinococcus).It contains brood

capsules with scoleces –Daughter cysts

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Taenia Solium(Pork tape worm)• Final host is man, intermediate host is pig. Larvae

is picked by the pig while scavenging• It moves through blood stream to the liver and

finally to active muscles where it forms cysts.• Active muscles include heart muscle, diaphragm,

massatter muscles, tongue, abdominal muscles, neck etc.

• This cystic form is know as cysticercus cellulosae.• The condition is know as cyticercosis. Also known

as pork measles.

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T. Solium

• It can be visible in muscles 4-10 weeks after infection

• They appear as white sports measuring 16x9.5mm.They look like as if rice is in muscles.

• In man, it causes neurocysticercosis leading to cns signs, epilepsy

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Pork Measles

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Cyst in the Peritoneal cavity

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Numerous cysts of C. cellulosae in the heart muscles.

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Cellulosae cysts in the liver.

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C. cellulosae cysts in the brain.

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T. SoliumJudgment at Meat inspection

• If the total number of cysts is more than 6, condemn the whole carcass.

• Any organ or head or any part of the pig with 1 or more cyst should be condemned.

• If in extended examination, you find between 1-5 cysts in whole carcass, conditionally approve.

• Subject the carcass to treatments such as -10oc for about 2wks

• Heat treatment-sterilize by heat or boiling at 95-100oc for 30 minutes or heat 72oc for 2hrs

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Prevention

• Massive chemotherapy treatment of infected humans,

• Improving sanitation. • Education humans are major ways to discontinue • Cooking of pork or freezing it and inspecting

meat are effective means to cease the life cycle• The management of pigs by treating them or

vaccinating them is another possibility to intervene .

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Taenia saginata(Beef Measles)

• Also called beef-tape worm• Or Beef measles• Cystic form called cyticercosis bovis• Big problem in Africa, asociated with serious

economical losses.We can not export meat.• Final host is man, intermediate host is

bovine(Cattle).Other wild ruminants are infected.

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Taenia saginata

• Taenia saginata occurs where cattle are raised by infected humans maintaining poor hygiene,

• human feces is improperly disposed of, • meat inspection programs are poor, • where meat is eaten without proper cooking

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Taenia saginata

• Predilection sites are tongue, heart muscle, massater, adductor muscles, diaphragm and psoas muscles, i.e. active muscles.

• Occasionally in liver and lungs.• The cyst is fully developed 18 wks after ingestion,

can be diagnosed at 6 wks, can remain viable even two weeks after death of animal.

• Uganda Code of Meat inspectors ensure routine inspection of tongue, masseters, heart, adductor muscles, etc

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Taenia saginataPostmortem findings :

• Small white lesions (cysticerci 2 – 3 weeks after infection) in muscle tissue

• Clear transparent bladders 5 × 10 mm (infective cysticerci, 12 – 15 weeks after infection, Fig. 91)

• Opaque and pearl like (over 15 weeks of infection)

• Degeneration, caseation and calcification (after 12 months or more after infection)

• Degenerative myocarditis

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C. bovis

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C.bovis

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C. bovis

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C. bovis

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Caseous cysticercus. Numerous clear transparent cysts on the heart surface. 0.6 mm in diameter in the heart muscle

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Cysticercus ovis. The heart of an old ewe showing heavy infestation with C. ovis. The cysts have degenerated and undergone calcification

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Taenia saginata Judgment at meat inspection

• Condemn the whole carcass if;– the infection is excessive i.e. if any muscle you incise,

you find 1 or more cysts or any organ you incise you find 1 or more cysts.

– The total number of cysts in any muscle or surrounding tissue or organ exceed 20 just on a single incision

– 10 or more cyst in a dressed carcass– 4 or more cysts in the head or organs of vicsera

together with 6 or more cysts in the dressesd carcass.

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Taenia saginata Judgment at meat inspection

• When there is discoloration of the carcass regard less of the number of cysts

• Conditionally approve if the carcass– Has 1-9 cysts– Any part of the carcass has 1 or 2 cysts

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Echinococcus granulosusHydatid disease

• The cystic form is hydatid disease• Final host is dog and other caniids• Intermediate hosts are cattle, ruminants, pigs, • Man is an accidental intermediate host• The eggs are released from the dogs into the

ground where they are picked• The larvae go through the walls of small

intestines and finally into the liver, lungs, peritoneal space, even in the brain.

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Adult worm.Echinococcuss

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Hydatid cysts in bovine liver

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Hydatid cyst in Brain

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Hydatid cysts

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Cystic hydatid disease

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Hydatid cysts in bovine heart. Note the detached germinal layer

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In liver of shoats

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hydatidosis

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Section of hydatid cyst,

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A person affected by hydatid disease

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Judgment at PM• The shape of cysts depend on shape and size of

organ where the cyst is located.• It can be spherical and can be very large• Leading to pressure necrosis.• Carcass showing emaciation, edema and

muscular involvement is condemned and destroyed.

• Affected viscera condemned and destroyed. Burying of carcass is not sufficient, since dogs may retrieve the affected organs.

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Taenia Hydatigena

• Its among the largest tape worms of dogs. The cystic form is cysticercus tennuicolis found intermediate hosts which are small ruminants(goats and sheep) and pigs.

• It is one of the largest cysts up to 7.5 cm with a long thin neck.

• Predilection sites include the omentum, mesenteries & liver. Its some times cold a bladder worm

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taenia hydatigena

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Cysticercus tenuicollis. Numerous subserosal cysts in the liver

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Taenia Hydatigena

• The development takes 5-6 weeks• Judgment

– If infestation is not heavy, since sub-serosally/ remove cyst and pass carcass

– In case of excessive infestation, condemn the affected organs.

– Man is an accidental host

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Taenia multiceps

• Cystic form is muliticpes multiceps or also called coenurus cerebralis

• It exclusively confined to brain tissue of ruminants

• Can be size of a pea or an egg. It has a transparent wall with many scoleces

• Animals get infected via contaminated water• Can be arrested in liver and die, otherwise reach

brain in 8-14 days leading to CNS signs

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Taenia multiceps

• Final host carnivores• Intermediate hosts- ruminants• Prevention

– Don’t give dogs raw meat

• Judgment– In early cases when there is no emaciation,

condemn the head– If there is emaciation, condemn the whole carcass

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Fascioliasis

• Caused by Fasciola hepatica, Fasciola gigantica

• Signs can be acute, sub acute and subclinical• At post mortem, acute lead to parachymatous

hepatitis, hemorrhages and fibrin on capsule.• The liver has numerous sharp small lesions,

which on pressure exudes semi fluid necrotic liver tissues and mature flukes.

• Although acute cases are rare

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Fascioliasis

• Chronic form most common• Bile ducts are thickened, dilated, calciferous• Bile ducts filled yellowish brown bile

containing flukes which can be expressed when ducts are incised.

• Excessive calcification and fibrosis of ducts leads to liver cirrhosis.

• Migrating flukes may reach other organs like lungs

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Numerous flukes of Fasciola hepatica observed in the bile ducts and liver parenchyma of a cow.

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Liverfluke

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Acute haemorrhagic tract in the bovine liver.

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Fascioliasis. Black parasitic debris in the liver

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FascioliasisJudgment

• Markedly cirrhotic liver should be condemned• Affected liver can be consumed for pet food• Or as inedible by-products or• Using in pharmacological industries for

producing heparin or Vit.B12• Otherwise mildly affected liver can trimmed

and pass the rest.

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Reading assignment

• Read and make notes on;– Lung worms eg (Dictyocaulus viviparus – Linguatura larvea– Oesophagostomiasis– Ascariasis

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