Veterinary Epidemiology and Zoonosis

TAENIOSIS

Synonym

• Cysticercosis (Taenia solium)

Type of zoonosis

• Food-borne zoonosis, Obligatory cyclozoonosis

Definition

• Taeniosis is an obligatory cyclozoonotic disease, caused by the intermediate stages of the tape worms Taenia solium and Taenia saginata. It is clinically characterized by abdominal pain, anorexia, nausea, diarrhoea and constipation, loss of body weight and debility. Nervousness and insomnia may also occur.

Etiology

• Taenia solium (tape worm of pigs) and Taenia saginata (tape worm of cattle)

Table: Differences between T.solium and T.saginata

Charateristic features	Taenia solium	Taenia saginata
Definitive host	Man and rarely dogs	Man
Intermediate hosts	Pigs and man In 60 to 70 days cyst develops, 110 days all cysts are fully developed	Cattle In 60 to 70 days cyst develops, 120 days all cysts are fully developed
Intermediate stage (larvae)	Cysticercus cellulosae (Measly pork)	Cysticercus bovis (Measly beef)
Predilection sites	Heart, diaphragm, internal masseter, tongue, neck, intercostals and abdominal muscles, less commonly brain, liver, lung, kidney and eye	Masseter, shoulder, esophagus, heart, tongue, diaphragm, liver, lung and lymph nodes
Disease in man	Taeniosis, Cysticercosis Autoinfection is possible in man and man can act as complete host	Taeniosis No autoinfection in humans

Reservoirs and incidence

• Human beings are universally susceptible to taeniosis.
• Infection is more common in low socio-economic group of the people.
• Prevalence of taeniosis is associated with socio-economic factors of the people, such as
  • Availability of carriers (pigs)
  • Poverty
  • Low literacy
  • Night soiling
  • Poor drainage
  • Unsanitized water supply
• Taenia can live in human intestine for many years.
• Eggs of Taenia can survive for about two months in summer and for 5 months in winter conditions.
• Use of untreated sewages for irrigation.
• Coprophagus insects and birds feeding on sewage water may disseminate infection to distance places.
• Humans get infection through ingestion of raw or under cooked meat and meat products infested either with Cysticercus cellulosae (Measly pork) or Cysticercus bovis (Measly beef).

Transmission and life cycle

Taenia solium

• Pigs (intermediate host) ingest gravid segments or free eggs in faeces of human beings. Human beings also act as intermediate hosts (autoinfection due to faecal-oral transmission).
• Oncospheres are released from the eggs in the intestine, which penetrate the intestinal wall and reach the blood circulation, and finally disseminated in to various tissues and organs.
• In 9 to 10 days, larvae (Cysticercus cellulosae – measly pork) fully develop in the different predilection sites, such as heart, diaphragm, internal masseter, tongue, neck, intercostals and abdominal muscles, less commonly brain, liver, lung, kidney and eye. This is the infective stage for human beings.
• Measly pork undercooked is consumed by humans results in emergence of larvae in the intestine, attachment and development in to adult parasite in 5 to 12 weeks time.
• Gravid segments (~8 to 10 gravid segments/day) and one gravid proglottid contains 30,000 - 50,000 eggs.

Taenia saginata

• Similar to Taenia solium, but no autoinfection in humans.
• Cattle (intermediate host) ingest gravid segments or free eggs from the pasture while grazing. The larvae develop (Cysticercus bovis – measly beef) in the different predilection sites, such as masseter, shoulder, esophagus, heart, tongue, diaphragm, liver, lung and lymph nodes.
• Man gets infection by ingesting measly beef undercooked. In the intestine it develops in to adult in 10 to 12 weeks and then voided in the faeces (50X10⁶ eggs in a month).

Disease in animals

• Animals act as intermediate hosts, in which the infestations are described as Cysticercus cellulosae (Measly pork) and Cysticercus bovis (Measly beef).

Disease in humans

• The incubation period is about 8 to 14 weeks. The infection is usually subclinical, however, in clinical cases; it is characterized by abdominal pain, anorexia, nausea, diarrhoea and constipation, loss of body weight and debility. Nervousness and insomnia may also occur.
• Cysticercosis is more serious than taeniosis in humans. It recognized as:
• Myocysticercosis: Muscular cramps, pain and muscle fatigue.
• Ocular cysticercosis: Presence of cysticerci in vitreous humor and anterior chamber of eyes leads to uveitis, iritis, retinitis and palbebral conjunctivitis.
• Neurocysticercosis: Signs depend on the location of the cyst found on the brain. Usually it found in the meninges, cerebral cortex and ventricles. So, symptoms of meningitis, epileptic encephalitis, headache, ataxia, nausea, vomiting and visual disturbances may be observed.

Diagnosis

• Based on clinical signs and history of the case.
• Examination of human stools
• Detection of coproantigen by ELISA and antigen profiling by SDS-PAGE.
• Biopsy examination, MRI or CT scan for the diagnosis of neurocysticercosis.

Treatment

• Praziquantel for cysticercosis
• Niclosamide or dichlorophen for taeniasis

Prevention and control

• Complete cooking of beef or pork.
• Strict post-mortem inspection and proper disposal of affected meat.
• Freezing of meat at -20C for 10 days
• Thorough washing of fruits and vegetables before consumption.
• Avoid night soiling.
• Maintain personal hygiene (washing hands always before eating).
• Treatment of sewage before disposal is important.
• Don’t allow coprofeeding of pigs.
• Chemoprophylaxis to kill adult parasites in the human intestine.
• Public health awareness.