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A Social Issue Neglected Tropical Diseases and Three Major Infectious Diseases

Cysticercosis

Cysticercosis is a parasitic tissue infection that occurs in areas in Latin America and Asia where hygiene infrastructure and practices may be underdeveloped. It is caused by larval cysts of the pork tapeworm. These larval cysts infect muscle, the eyes, the brain, and/or other tissue. When the infection reaches the brain it causes serious symptoms like hydrocephalus, which can be fatal.

Causes of Infection

Disease Agent

Larval cysts of the pork tapeworm

<Head of pork tapeworm parasite in a pig> CDC

Intermediate host

Pigs

Humans acquire the tapeworm infection after eating undercooked pork contaminated with cysticerci, the larval form of Taenia solium. When ingested, the cysticerci attach to the intestinal wall as they reach the small intestine, there developing into adult tapeworms and laying eggs. Sometimes, the oncosphere that emerge from these eggs then invade other via intestinal blood vessels in what is known as autoinfection and live in internal organs then developing into cysticerci. Family members may also acquire cysticercosis after ingesting eggs shed in excretions of an individual who has an intestinal adult tapeworm infection. The larval cysts can be formed in the muscles and other organs as well as the brain.

Symptoms

The symptoms usually occur when the cysticerci are dying. Therefore, occasionally no symptoms appear for several months to several years after initial infection. Depending on where the cysticerci die in the body, different symptoms may also appear. Further, depending on where these cysticerci occur, they may become space-occupying lesions (SOL) and cause intracranial pressure.

When cysticerci die in the muscles

Cysticerci in the muscles do not generally cause symptoms. However, people may become aware of mass felt under the skin.

 
When cysticerci die in the eyes

Although rare, cysticerci may float in the eye and cause blurry or troubled vision. Eye infections may further cause swelling or detached retina.

 
When cysticerci die in the brain or spinal cord

In such cases, this is referred to as neurocysticercosis. The symptoms of neurocysticercosis depend on where and how many cysticerci are found in the brain. Seizures and headaches are the most common symptoms in all cases. Other symptoms may also occur, including lack of attention during social interactions and to one’s surroundings, difficulty balancing, and hydrocephalus. Neurocysticercosis can also result in death. However, even when the cysticerci do not die, they can still cause elevated intracranial pressure depending on where and how many of them are present (see above).

 

Diagnosis and Treatment

Diagnostic Methods

Several tests are performed to diagnose this disease, including fecal examinations, immunological tests, and brain MRI/CT scans. The presence of a subcutaneous mass is sometimes important in diagnosis.

 
Treatment

Cysticercosis is treated with praziquantel and/or albendazole as well as corticosteroids and/or anti-epileptic drugs as supporting therapies. When these treatments have no effect, the cysticerci must be surgically removed.
As edemas and other symptoms disappear as the cysticerci die and calcify, when the infection is confirmed to be only in one location, the disease can be left untreated. However, anti-epileptic drugs are recommended in cases where a calcified lesion causes epileptic attack.

 

Prevention

Preventive measures against cysticercosis include:

  • Heating pork for a sufficiently long period of time before eating
  • Educating all residents in particular children about the importance of washing their hands with soap and warm water after using the toilet, changing diapers, or before touching food

Regions at High Risk of Infection

Cysticercosis is most often found in rural areas in developing Latin American, Asian, and African countries where sanitation infrastructure or practices may be poor and where pigs are allowed to roam freely.

Estimated Number of Infected People

Neurological symptoms, such as epilepsy, appear when people are infected with cysticercosis. An estimated 50 million people are affected by epilepsy. More than 80% of these people live in countries where there are a large number of low- to lower-middle income families. Many of these countries have endemic T. solium infections in both humans and pigs, which strongly implies a correlation between incidents of epilepsy and T. solium infections in humans and pigs.

Estimated Number of Deaths

Although there is limited data on deaths from cysticercosis infection, 221 cysticercosis deaths were reported in the United States in the 12 years between 1990 and 2002. Most of the victims were immigrants from Latin America.

Initiatives by Pharmaceutical Companies and NGOs

Cysticercosis was added by WHO (World Health Organization) to its list of NTDs in 2010, although it was in 1993 that the disease was declared eradicable by the International Task Force for Disease Eradication. An interagency meeting of WHO, the FAO(Food and Agriculture Organization of the United Nations) and OIE(Office International des Epizooties in French) on the planning, prevention and control of neglected zoonotic diseases was held in 2011 and targeted cysticercosis/taeniasis as a top priority disease of global importance. Validating a strategy for the control and elimination of T. solium cysticercosis/taeniasis by 2015 was subsequently made a medium- and long-term goal. The strategy of eliminating the disease in selected endemic countries by 2020 is now in place.

References
WHO- Neglected Tropical Diseases, accessed March 19, 2014,
http://www.who.int/neglected_diseases/mediacentre/factsheet/en/
CDC- Neglected Tropical Diseases, accessed March 19, 2014,
http://www.cdc.gov/globalhealth/ntd/diseases/