Pig Parasites of public health importance Flashcards
Name 3 zoonotic parasites of pigs
- Trichinella spiralis
- Taenia solium
- Balantidium coli
Name the protozoal parasite of pigs
Cystoisospora suis
Name a mite of pigs
Sarcoptes scabei
Name a louse of pigs
Haematopinus suis
Describe the two groups of Trichinella spp
- Encapsulated/encysted
- Non-encapsulated/do not encyst
Which spp of Trichinella is the main aetiological agent of Trichinosis?
Trichinella spiralis
Which spp are hosts of Trichinella?
Wide range of hosts
- All types of animals but amphibians
- Pigs, horses, humans
- Carnivores!
Describe the worldwide distribution of Trichinella
Everywhere but Antarctica
Describe the features of Trichinella spiralis and its life cycle
Intracellular nematode
No eggs or larvae in faeces
No free living stages
Describe the females/eggs of Trichinella
Females are larviparous
L1 – Newborn larvae (NBL)
Which stage of Trichinella is infective?
L1 muscle larvae
How do animals become infected with Trichinella?
Ingesting contaminated meat that contains the L1 muscle larvae
Where does L1 - L5 development of trichinella occur?
In the small intestine
Describe what happens to the L1 larvae of Trichinella after they are ‘born’ including how they become infective
NBL (L1) born, migrate in blood and lymphatic system to skeletal muscle, invade a single muscle cell = muscle larvae (ML)
Parasite forces a terminally differentiated muscle cell to go back into the cell cycle so the parasite can grow – deposition of collagen around itself to create the cyst – the parasite stays as an L1 throughout this process
What is a nurse cell?
Muscle cells infected by a single muscle larvae
Which spp are affected by Trichinella disease?
No disease in domestic animals but can cause serious disease in humans
How does infection of trichinella occur?
Infection occurs by the consumption of raw or undercooked contaminated meat Main sources of infection: - Pigs and horses - Game meat - Arctic animals
What are the clinical signs of Trichinella?
Typical trichinosis symptoms: abdominal pain, diarrhoea, fever, chills and peri-orbital oedema
Severe cases – myocarditis, encephalitis, secondary infections (pneumonia) and even death
How is Trichinella diagnosed?
- Microscopic examination of biopsy samples
- Identification of larvae digested from muscle tissue using HCl-pepsin
How is Trichinella treated?
- Albendazole/mebendazole
- Early diagnosis and prompt treatment can kill adults and prevent release of NBL
- Once larvae established in muscle cells treatment may not eliminate infection and associated symptoms
How is Trichinella controlled?
- All breeding pigs (sows and boars) and pigs from non-controlled housing must be tested at slaughter for Trichinella
- Wildlife are important reservoirs – monitoring using indicator animals (foxes and racoons)
- Cooking at least 70 degrees (and freezing) meat will kill Trichinella parasites in most cases
Name the pork tapeworm
Taenia solium - not in the UK
What are the two routes of infection in people for Taenia solium?
- Ingesting cysts in undercooked pork
- Ingesting eggs
What are the symptoms of Taenia solium when cysts have been ingested?
How long after ingestion do signs develop?
Abdominal pain, nausea, diarrhoea or constipation may arise - ~ 8 weeks after ingestion of meat containing cysticerci
What are the symptoms of Taenia solium when ingestion of eggs & development of metacestode stage have occured?
Cysts in muscle – generally no symptoms
Cysts in central nervous system – neurocysticercosis
Describe the signs of neurocysticercosis
- Focal epilepsy, epileptic seizures, hydrocephalus, chronic headaches, focal deficits and symptoms associated with increased intracranial hypertension
- T. solium is the cause of 30% of epilepsy cases in endemic areas
Why is Taenia solium not seen in the UK?
Due to good sanitation and meat inspection
Name the ciliated protozoa found in the large intestine of pigs
Balantidium coli
Describe the features of Balantidium coli and its disease
- Important zoonosis, cause of intestinal disease in humans: pigs main animal reservoir
- Faeco-oral transmission
- Cyst and trophozoite stage
Describe the life cycle of Balantidium coli
Cyst is ingested and within the SI the parasite encysts, becomes a trophozoite and then multiplies by binary fission
A proportion of the trophozoites will then encyst and then become the cyst stage which is passed out in the faeces to continue the life cycle
Name the parasite that causes coccidiosis in pigs
Cystoisospora suis
In what conditions does Cystoisospora suis occur?
- Both indoor and outdoor production systems
- In summer: sows with heavily contaminated udders from wallowing
- Wet weather: beds not renewed between batches.
Describe the disease and its presenting signs caused by Cystoisospora suis
- Most common cause of scour in piglets 10-20 days old
- Scouring seen in all or part of litter – yellow/cream looking, with possible blood flecks
- Presents as diarrhoea that is unresponsive to antibiotics
- Reduced weaning weights & possible secondary post-weaning enteritis
Describe the life cycle of Cystoisospora suis
Infection – ingestion of sporulated oocysts (20µM – smaller than in dog and cat spp)
Small intestine - 2 rounds of asexual reproduction
Sexual reproduction – micro and macro-gametocytes that produce zygote = oocyst.
Self limiting
What is the PPP of Cystoisospora suis
5days
How is Cystoisospora suis diagnosed?
Clinical signs – strong indication of coccidiosis
Often low or negative oocyst counts – not definitive
How is Cystoisospora suis treated?
- Sulphonamides at 3, 10 and 17 days old
- Toltrazuril – one dose, preferably at 4-5 days old
What are the considerations when treating Cystoisospora suis with Toltrazuril?
- Early before gut damage: prevent clinical disease
- Late infection: destruction of C. suis triggers an immune response protecting from future infections
- 77 day meat withdrawal period: recorded in medicines records.
How is Cystoisospora suis controlled?
Indoor - removing contaminating oocysts from environment, resistant to most conventional disinfectants but lime washing effective.
Outdoor - arcs must be moved between consecutive farrowings and boards should be avoided
Describe the features of Sarcoptes scabei
- Burrowing mite, spends entire life cycle on the host
- Lays eggs in tunnels within the skin
- Life cycle (all stages within epidermis): 10-15 days
What are the clinical signs of a Sarcoptes scabei infection
- Lesions commonly start around the ears, spread to back, flanks and abdomen
- Severe immune reaction, pruritis and erythema.
- Intense itching, thickened skin, head shaking, secondary bacterial infections
How is Sarcoptes scabei transmitted?
direct contact - sow to piglet
How is Sarcoptes scabei treated/prevented?
Treat/prevent with MLs – in feed or injectable (depending on time of slaughter)
Cleaning/disinfecting wooden and concrete surfaces
Describe the features of Haematopinus suis
- Sucking louse
- Only louse found on pigs: common, present at low levels
- Nymphal lice - around the ears and skin folds of upper legs
- It’s really large!! (5-6mm)
- Egg to adult form – ~4 weeks
What are the signs of Haematopinus suis
- Itching, reduces feeding and growth rates and also affects hide value
- Blood sucking parasite: anaemia in piglets, viral infections (PRRS, PCV2 & Swine pox) from pig to pig
Name two parasites of pigs that are zoonotic and that could be detected at slaughter
Trichinella spiralis and Taenia solium
Why is the life cycle of Trichinella spiralis unusual for a nematode parasite?
Intracellular parasite. No free-living stages and no eggs/larvae passed in faeces. Transmission by ingestion of L1 in muscle – carnivorous life cycle. Female worms are larviparous.
How do pigs become infected with Taenia solium?
Ingestion of embryonated eggs or gravid proglottids released into the environment in human faeces.
How might you detect and control an outbreak of Sarcoptes spp. in a group of indoor pigs?
Diagnosis based on clinical signs of acute pruritis, thickened skin, head shaking and secondary bacterial infections and deep skin scrapes to find the mites. Treat with injectable/ in feed ivermectin. Ensure housing is cleaned effectively to remove contamination.
