Sustainable Control of Zoonotic Parasites

Question 1

Neglected zoonoses.

Answer 1

Cystic echinococcus.
Leishmaniasis.
Cysticercosis.
Trypanosomiasis.

Question 2

1. What parasite causes cystic echinococcosis?
2. What sp. are the definitive hosts?
3. What spp. are the intermediate hosts?
4. AKA?
5. Effect on humans?
6. What is the PPP?
7. How do dogs become infected?

Answer 2

1. Echinococcus granulosus.
2. Canines.
3. Ruminants, horses, humans.
4. Hydatid disease.
5. Zoonotic caught via dog faeces.
6. 40-50 days.
7. Consumption of offal from fallen stock.

Question 3

How can cystic echinococcosis be controlled?

Answer 3

• Prevent dogs scavenging carcasses.
• Avoid feeding uncooked offal to dogs.
• Prev. med Praziquantel for dogs. – every 28-42 days for dogs in endemic areas – obligatory for dogs before entering UK to prevent entry of E. multilocularis.
• Hygiene e.g. hand washing after touching dogs.
• Public info campaigns.
• Vac – trials.

Question 4

1. Dog vac against echinococcosis.
2. Ruminant vac against echinococcosis.

Answer 4

1. Oral recombinant E. granulosus vac.
   70-80% decrease of parasite burden in vac dogs.
   Slower development rate in all remaining worms.
2. EG95: cloned recombinant antigen from parasite oncosphere.
   96-98% protection of sheep against experimental challenge w/ E. granulosus eggs.
   90-99% protection of cattle for 12 or 23 months after 2 or 3 doses respectively.

Question 5

1. What parasite causes alveolar echinococcosis.
2. What spp. are the definitive hosts?
3. What spp. are the intermediate hosts?
4. AKA?
5. Mechanism of infection in humans.
6. Define sylvatic cycle.
7. PPP?

Answer 5

1. Echinococcus multilocularis.
2. Canines (dog, fox, coyote) and cats.
3. Rodents and humans.
4. Alveolar hydatid.
5. Via dog faeces.
6. Parasite is maintained in wildlife.
7. 30 days.

Question 6

How can alveolar echinococcosis be controlled?

Answer 6

Prevent access of dogs and cats to rodents?
– impractical.
Hygiene.
– Around household pets – impractical?
– Rubber gloves when handling fox or wolf skins/furs.
– Thorough washing of forest fruits and berries in endemic areas.
Preventative Praziquantel for dogs and cats.
– Every 28 days in endemic areas.
– Anthelmintic baits for wild and stray definitive hosts, e.g. foxes?
Post-Brexit UK Government Regs for Pet Travel.
– Proven effective.
– Obligatory before entry to UK.
– Tx of dog given and certified by vet.
– Within 5 days prior to travel (but >24h).
– Also necessary within 5 days prior to short trips abroad –> no return w/in 24h and retreatment after 28d.
– Does not kill the eggs.
– First defaecation of dog in UK produces potential for infection of rodents and predator foxes.
– Risk of introduction reduced but remains present!

Question 7

1. What parasite causes taeniasis/bovine cysticercosis?
2. What sp. is the definitive host?
3. What sp. is the intermediate host?
4. AKA?
5. Define cysticercus.
6. Why is it referred to as a cysticercus?

Answer 7

1. Taenia saginata.
2. Humans.
3. Cattle.
4. Beef tapeworm.
5. Larval tapeworm at a stage in which the scolex (anterior end) is inverted in a sac, typically found encysted in the muscle tissue of the IH.
6. Originally thought to be a genus, before relationship to adult tapeworm (Taenia sp.) in DH was elucidated.

Question 8

Life cycle of Taenia saginata.

Answer 8

Egg in faeces > embryonated eggs and ingested proglottids (cow) > Hexacanth embryo penetrates intestine (cow) > into bloodstream (cow) > cysticercus in muscle (cow) ingested by human > scolex latches to s. intestine (human) > adults in s. intestine > shed in faeces.

Question 9

1. How long is adult taenia saginata in human?
2. Describe scolex.
3. Clinical signs in humans?
4. Why is Taenia saginata infection undesirable in humans?
5. Persistence in humans?

Answer 9

1. 5-15cm long.
2. No hooks or rostellum – “unarmed”.
   – Distinguishes from T. solium and other Taenia spp.
3. Usually asymptomatic. Occasionally diarrhoea or hunger.
4. Aesthetic – motile proglottids or entire tapeworm passed in the stool.
5. Persists in industrialised and low-middle income countries.

Question 10

1. Clinical signs of bovine cysticercosis?
2. What causes bovine cysticercosis infection in cattle?
3. How does this infection cause financial losses to the cattle industry?

Answer 10

1. Usually symptomatic.
2. Contamination of pastures (or feed) by improperly treated wastewater, sludge or human faeces.
3. Downgrading, condemnation, extra handling, freezing and transport of infected carcasses.

Question 11

How can bovine cysticercosis be controlled?

Answer 11

Transmission prevention.
– Thorough cooking of beef.
– Comply w/ regs on treatment and use of wastewater and sludge.
Meat inspection, followed by condemnation or freezing treatment, when necessary, as prescribed by legislation.
– Visual inspection of specific muscles.
– Incisions in internal and external masseter muscles (cattle >6wks).
– Lengthwise incision of the heart (all ages).
– Carcasses and offal of heavily infected animals are condemned.
– Lightly infected cattle have affected parts condemned and the remainder of carcass undergoes freezing treatment to inactivate cysticerci.

Question 12

1. What parasite causes Taeniasis cysticercosis / neurocysticercosis?
2. What sp. is the DH?
3. What spp. are the IHs?
4. AKA?

Answer 12

1. Taenia solium.
2. Humans.
3. Pigs, humans.
4. Pork tapeworm.

Question 13

1. Length of adult taenia solium in human host and where does it reside?
2. How many eggs does the adult taenia solium release each day?
3. What is the parasite referred to in the pig host?
4. What if human accidentally infected w/ T. solium metacestodes?

Answer 13

1. 3-5m long – in s. intestine.
2. > 50,000.
3. Cystercercus cellulosae. It is a metacestode.
4. CNS infection, epilepsy common.

Question 14

How is T. solium cysticercosis potentially eradicable?

Answer 14

Humans are the only DH.
Pigs are the only IH.
Human tapeworm infections are sole source of infection for IH pigs.
Domestic pigs can be managed.
No wildlife reservoirs exist.
Safe and effective chemotherapy available.

Question 15

Detection of T. solium taeniosis in humans.

Answer 15

Observation of proglottids in stool.
– low sensitivity.
Routine coprology.
– low sensitivity (10%).
Coproantigen detection.
– more sensitive.
Serology.
– Enzyme-linked immunoelectrotransfer blot (EITB).
– Specific for T. solium infection-related antibody.
– Being validated currently.

Question 16

Detection of T. solium cysticercosis and neurocysticercosis in humans.

Answer 16

Biopsy of SC nodules.
Neuroimaging.
– Routine radiography.
– CT and MRI scanning.
Immunodiagnostics.
– Antibody tests – exposure.
– Antigen tests – active infection.
Autopsy.

Question 17

Detection of taenia solium in pigs.

Answer 17

Antemortem diagnosis.
- Lingual exam (sensitivity <50%).
- Antigen detection.
– cross-reaction w/ Taenia hydatigena.
- Antibody detection.
– May not have active exposure.
– Maternal antibodies in young pigs.
Post-mortem diagnosis.
- Slaughterhouse surveys (biased?).

Question 18

1. Treatment of human taeniosis.
2. Treatment human cysticercosis.
3. Treatment of porcine cysticercosis.

Answer 18

1. Praziquantel (5-10mg/kg single dose).
   Niclosamide (2g single dose).
2. Praziquantel (50mg/kg daily x 15-30 days).
   Albendazole (15mg/kg daily x 8-30 days).
3. Oxfendazole (30mg/kg P.O. single dose).

Question 19

Strategies of intervention for T. solium.

Answer 19

Cook meat.
Control slaughter.
Meat inspection.
—————————————
Mass taeniacidal treatment.
Improve sanitation.
—————————————
Restrain pigs.
Treat pigs.
Vaccinate pigs.

Question 20

6 easy steps to break the pork tapeworm cycle.

Answer 20

1) Always use a toilet.
2) Wash your hands.
3) Go to clinic.
4) Stop pigs from roaming.
5) Check meat is safe.
6) Cook meat well/

Question 21

Control options for T. solium.

Answer 21

• Mathematical modelling of transmission useful to identify potential impact of various control strategies.
• Mass treatments may give a good impact in the short term.
• Long-term impact of mass treatments is limited
• Reduction in basic transmission conditions is needed to give long-term reduction in prevalence.
• Combo of approaches may be the only way to control/eradicate T. solium infections.
• Vaccine for pigs, but logistical challenges to administration.

Question 22

1. What parasite causes diphyllobothriosis / fish tapeworm?
2. DH?
3. IH?

Answer 22

1. Diphyllobothrium latum.
2. Humans.
3. Crustaceans, fish.

Question 23

Diphyllobothrium latum life cycle.

Answer 23

Un-embryonated eggs pass in human faeces > Eggs embryonate in water > Coracidia hatch from eggs and are ingested by crustaceans > Procercoid larvae in body cavity of crustaceans > infected crustacean ingested by small freshwater fish > Procercoid larva released fro crustacean and develops into plerocercoid larva > Predator fish eats infected small fish > Human ingests raw or undercooked infected fish > Adult diphyllobothrium latum in human s. intestine > Proglottids release immature eggs into human intestine.

Question 24

1. Length of adult diphyllobothrium latum infecting humans.
2. Amount of eggs released by adult diphyllobothrium latum adult into human?
3. Cause of increasing incidence of diphyllobothrium latum in humans?
4. How many infected worldwide?

Answer 24

1. Up to 10m.
2. ~ 1 million / day.
3. Increasing popularity of raw fish.
4. 20M.

Question 25

1. Diphyllobothrium latum human infection clinical signs.
2. Complications?
3. Prevention of transmission to humans?
4. Meds for prevention?

Answer 25

1. Asymptomatic mostly.
   Some symptoms can include abdominal pain, V + D, weight loss, vitamin B12 deficiency leading to megaloblastic anaemia.
2. Due to intestinal obstruction and gall bladder disease caused by migration of proglottids.
3. Cooking or freezing fish.
4. Praziquantel or niclosamide,

Question 26

1. What parasite causes trichinellosis?
2. Hosts?
3. Diagnosis in slaughter pig meat?
4. Life cycle?

Answer 26

1. Trichinella spiralis (nematode).
2. Wide host range.
3. By microscopic examination of HCl/pepsin digest for larvae.
4. Ingestion of undercooked meat > Larvae released into human s. intestine > Adults in human s. intestine > Larva deposited in mucosa > Encysted larva in striated muscle.