Posted by: glamielle | August 21, 2010

Echinococcosis prevention in the highlands of Peru

The communities studied were often remote and had limited access to medical facilities

Zoonotic diseases most often affect populations of the developing world, as exampled by tuberculosis, an illness largely eradicated from developed countries but still present in poor communities. The relationship between poverty and such diseases are multifactorial in nature but heavily influenced by lack of education, inadequate funding or little international interest in these pathogens.

I was able to witness these relationships as a 4th year veterinary student at Western University. Our curriculum enabled us to set up rotations in specific areas of interest and I naturally focused on public health. During one of these rotations, I and two other classmates spent one month in Peru with the San Marcos Veterinary Faculty in Lima, Peru. We participated in various local research projects regarding zoonotic diseases such as Chagas disease, neurocystisercosis, equine infectious anemia and methicillin-resistant Staphylococcus aureus (MRSA) prevalence in neighboring farms.

Our main work, however was in the Peruvian Highlands as we were actively participating in a prevention program against tapeworm Echinococcus granulosus. This is a parasites that is distributed worldwide, however there are several hotspots such as Peru, where human prevalence is thought to be around 9% in some parts of the country (one of the highest worldwide). Other hotspots include Northern Africa and China.

Life cycle of Echinococcus granulosus (http://www.dpd.cdc.gov/dpdx/html/Echinococcosis.htm)

The parasite’s life cycle is closely related to several domestic species, which greatly facilitates human transmission. Dogs are the primary host and the pathogens are shed in the feces. From there, they are eaten by a secondary host, in our case sheep, and escape the gastrointestinal tract to internal organs where they form cystic structures. This life cycle completes when dogs eat these organs along with the cysts.

A human radiologist came along for part of the research to help us identify hepatic hydatid cysts in sheep

Dogs remain relatively asymptomatic for infection as the parasite stays in the intestines, however sheep can show clinical signs as these cysts grow and obliterate internal organs.

In the Andean context, this life cycle is favored by a sheep-based agriculture and a large canine population, mainly used as herders. Native practices of home slaughtering of the sheep and feeding viscera to the dogs also greatly facilitate this life cycle. Human cystic echinococcosis is similar to the sheep disease as people are considered a secondary dead-end host (fortunately because we seldom get eaten by dogs, the life cycle doesn’t complete itself after human infection). The pathology is also similar in the sense that the tapeworm disseminates to internal organs, mainly liver and lungs, and forms slowly growing cystic structures, eventually leading to failure of these organs. In the Andean context, children are often the primary caretakers of the dogs and thus are at higher risk of exposure.

People often get infected at an early age as they care for the family’s dog

Diagnostics in people and sheep is most efficiently done through diagnostic imaging such as abdominal ultrasounds or radiographs. Treatment is often difficult as medications can have difficulties reaching through the cysts and surgery is often necessary for complete removal. However, surgery itself is not without risks and rupture of the cyst during removal can cause dissemination of the parasites throughout the body and secondary cyst formation in the abdomen. Several methods have been developed to treat the infection such as the perforation aspiration injection and re-aspiration (PAIR) procedure, in which cystic fluid is aspirated and then replaced by medication. This procedure, however requires general anesthesia and advanced medical equipment, which is not always available in remote areas. In fact, in the some remote communities of the Andes, medical facilities can be virtually non-existent and infection in people can be undiagnosed until later stages.

Diagnostics in dogs can also be difficult since these animals are usually asymptomatic. Fecal floatation for egg identification can yield results, however, eggs are shed intermittently and it is impossible to distinguish them visually from other tapeworm eggs such as Taenia spp. Other methods include ELISA and PCR but these can be costly. The infection in dogs is efficiently resolved through the uses of praziquantel but, since the parasite is present in the environment, there are high rates of re-infection.

The culprit: Echinococcus granulosus, in a heavily infected canine fecal sample

Our work with the San Marcos Faculty included travelling to various Andean communities to promote knowledge of the

Fecal sampling in a dog. Samples will be analyzed for infection through fecal floatation and copro-ELISA

infection and its life cycle as well as testing alternate treatment protocols using more frequent praziquantel administration. We took blood and fecal samples from dogs presented to us by the villagers and gave them medication. Researchers would come at different time in the future to reproduce these steps and measure rates of re-infection in dogs. Along with that, I designed a knowledge, attitude, practices (KAP) survey to identify potential risk factors for human infection and administered the survey in a few of these communities. The fact that these were usually indigenous populations often made Quechua the favored language compared to Spanish and communications often required a translator. I found that knowledge of the disease was inconsistent and education is the first barrier for proper management and control of echinococcosis in these parts.

When considering zoonotic diseases, prevention is one of the most important aspects for eradication and control. These are often pathogens that are prevalent in parts of the world that do not have proper access to medical professionals, proper educational background or the economic power to implement ideal surveillance programs. In this context, there are specific practices that put people at higher risk of infection, namely feeding infected sheep offal to dogs or hygiene habits. If we want to be able to prevent human infection, we must educate the local population about the disease and implement proper slaughter protocols to break the life cycle of the parasite. A One Health approach is needed to recognize that reduction of disease in people is impossible without treating dogs and the environment in which they live and thus limit rates of re-infection.

While there is a lot of attention on emerging infectious diseases such as novel influenza strains or Ebola virus, we need to remember that there are countless chronic or re-emerging illnesses diseases that still affect millions of people worldwide, such as cystic echinoccocosis or leptospirosis.

Administering KAP surveys. Contact with the affected population was an essential part of the project.

More information:

Echinococcosis – Iwoa State Center for Food Security and Public Health

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