Travis had a blast exploring Lighthouse Cave on San Salvador, Bahamas. See other beautiful phenomena from the Bahamas.
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The Not So Romantic Kissing Bug: Chagas Disease and its Effects on Costa Rica
As I curiously explored the CDC (Center for Disease Control) website for the prevalent diseases of Costa Rica, I stumbled upon Chagas diseaseÑa disease that I learned a little bit about this past semester in an ecology class. This disease, transmitted by Triatoma dimidiata (also known as the kissing bug), has a variety of ecological consequences. It is detrimental to human health, and other mammals such as dogs and many rainforest species. The disease has also been established in the food and water supply, and is continuing to spread. Chagas disease is an important and interesting one to study.
An endoparasite, called Trypanosoma cruzi (which is a flagellate protozoan), is responsible for Chagas disease. It is transmitted to humans through food, water, blood transfusions, organ replacements, fetal transmission and through breast milk. However, humans most commonly contract the disease via insect vectors, the most common being the kissing bug. The kissing bug is an inch-long blood-sucking insect, which has a unique method of attack. Because they are a nocturnal species, they will come out of their hiding places late at night in search of a blood meal, and suck the blood from their victimÕs lipsÑhence its nickname the kissing bug. The kissing bug tends to defecate and urinate immediately after eating which exposes the Chagas parasite. Usually, the parasite finds its way into the bite wound, and leaves the victim infected (Smith).
The kissing bug can be found in the in Central and South America in a variety of habitats. Their endemic habitat consists of the trees of rainforests where they thrive off of the blood of birds and rainforest mammals. As humans continue to demolish natural rainforest habitats, the kissing bug has adapted to live in cracks and crevices of walls and roofs of sub-standard housing on the outside of the rainforests, especially poorly constructed housing made from Òmud, adobe, or thatchÓ (Chagas Disease). Because of this redistribution of the kissing bug, humans along with domesticated and feral animals (such as dogs) outside the rainforest perimeter are now more at risk of becoming in contact with the kissing bug.
An infection of the parasite T. cruzi can cause an assortment of symptoms. The acute stage, which is usually fairly mild, is most often seen in children. However, symptoms can include Òfever, lymph node swelling, enlargement of the liver or spleen, and fatigueÓ (Chagas Disease). Swelling around one eye (Romana's sign) may occur if insect feces are rubbed into the eye (Chagas Disease). Interestingly enough, most of the people who are infected do not show any initial symptoms.
When an infected person enters the chronic phase, when Òfew or no parasites are found in the bloodÓ they are usually unaware that they are still infected (Disease). During the chronic phase, Òmany people may remain asymptomatic for life and never develop Chagas-related symptoms. However, Òan estimated 30% of infected people will develop debilitating and sometimes life-threatening medical problems over the course of their livesÓ (Disease). Usually, about Òten to twenty years later, about one-third of those infected show evidence of irreversible damage to the heart, esophagus, or large intestineÓ (Chagas Disease). In Costa Rica it is most common for the parasite to lodge itself into the heart muscle, and when the parasite is activated it begins to eat the muscle. Eventually, Òthe tissue becomes so thin it simply bursts from normal vascular pressureÓ (Smith). Unfortunately many of these situations are misdiagnosed as heart attacks. The cardiac symptoms can include Òabnormal heart rhythms, heart failure, angina, left ventricular aneurysm, and cardiac arrestÓ (Chagas Disease). This heart arrhythmia can cause sudden death because the heart becomes dilated and cannot pump blood efficiently (Disease). Other symptoms include Òesophageal involvement may lead to difficulty swallowing and malnutritionÉintestinal involvement may cause constipation and abdominal distentionÓ (Chagas Disease). With this collection of symptoms, the disease can be fatal, especially for people with AIDS and people with suppressed immune systems because ÒChagas disease can reactivate with parasites found in the circulating bloodÓ (Disease). It has been estimated that as many as 8 to 11 million people in Mexico, Central America, and South America have Chagas disease, most of whom do not know they are infectedÓ (Ortho-Clinical Diagnostics Receives FDA Approval for First Blood-Screening Test for ChagasÕ Disease). Overall, this disease now infects 16 to 18 million people, and there are 1 to 3 million new cases per year.
Symptoms among other mammals are similar to those in humans. Because of this, infected animals are used to research the disease and possible treatments for humans. In most cases dogs go through acute and chronic stages, like humans. Dogs usually are not diagnosed until the chronic stages, and it is typical for the dog to present with some sort of heart failure (Montenegro). In one study, conducted through the School of Veterinary Medicine in Costa Rica a group of 54 pet dogs were assessed concerning Chagas disease. This study was unique in that the sample included dogs from various types of communitiesÑwealthy and poor. It is also interesting to note that a dog belonging to wealthy owners creates a reservoir for the disease in wealthy communities.
Although there is not a vaccination for Chagas disease, there are a few treatment options available. There are antiparasitic and symptomatic treatments which both can be essential to prevent fatality. The antiparasitic treatment is Òmost effective early in the course of infection but is not limited to cases in the acute phaseÓ (Disease). The symptomatic treatment can help people who are experiencing cardiac or intestinal problems, such as pacemakers and medications for irregular heartbeats (Disease). Alternative treatments are also being looked into. One doctor spent time with the Bribri and Guaymi communities and learned how their Òcuranderos,Ó or ÒhealersÓ use plants to treat different ailments. He learned that one could treat symptoms of this disease by drinking Òa cup of tea [from the gavilana plant] every day until the eye is no longer swollen and there is no more feverÓ (Santenello).
While the rainforest provides a tea plant to treat symptoms of Chagas disease, the disease in turn ironically has adverse effects on the rainforest. The disease decreases rainforest biodiversity as it attacks birds and mammals. The rate of infection is accelerated by habitat fragmentation. As humans continue to pursue deforestation, the rainforest becomes fragmented into smaller areas, which changes biotic and abiotic factors of the ecosystem. Biodiversity decreases overall and the potential hosts for the disease are at greater risk. They are more compact which provides more rapid transfer. In one study observing Òthe effect of the fragmentation process on Trypanosoma cruzi infection among small wild mammals,Ó continuous forests compared to fragmented forests revealed that Òmarsupials were less abundant than rodents in the continuous landscapeÉan overall decrease in small wild mammal richness was observed in the smaller fragmentsÓ (Vaz). It has been observed in various studies that primates and marsupials, especially the opossum, seem to be a favorite victim for the kissing bug, and ultimately the species at greatest risk for contracting Chagas disease.
As the disease continues to spread and become more abundant, food and water sources are becoming contaminated, which in turn accelerates the disease spread even further. Food and water becomes contaminated when the kissing bug or other vectors or pieces of the vectors are accidentally incorporated into the food or water, or when the bug feces get into the food or water. According to one source, between June 2006 and August 2007, Ò116 people have caught the disease after drinking fruit juices typical of the region, mainly those made from the berries of the acai and bacaba palms, in which the vector had been accidentally ground upÓ (Doyle). This source argues that Òfood borne infection can only be controlled by hygienic measures making sure that fruits contaminated with triatomid bug feces are not used for human consumptionÓ (Doyle).
It is absolutely necessary for Costa Rica to take the measures necessary to maintain clean food and water. This, along with other sources of prevention, can make a difference in halting the spread of this disease. Other preventative measures include stopping the spread between vector to human, and stopping the spread between human to human. Costa Ricans should take care to increase cleanliness and hygiene. If action were taken to help the poor to establish cleaner and more customary housing, then these people are not forced to coexist with the disease carrying kissing bug. MD travel health recommends the use of Òbed nets and insecticides to prevent transmission.Ó Also, there have been efforts to enforce the screening of blood and organ donations for Chagas. It is also recommended for mothers who are nursing to make sure their nipples are not cracked or chapped. These methods would prevent the spread of disease between humans. There are also some Òlarger pictureÓ techniques that could be enforced to help prevention. One source suggests Òincreasing human population density, rain forest deforestation, and human predation of local fauna are risk factors for human T. cruzi infectionsÓ (Teixeira). Unfortunately, these are three of the major problems for rainforest survival, and the factors are also contributing to the spread of disease which gives even more reason to control these human-initiated problems.
There have been efforts to globalize the prevention of Chagas disease. The World Health Organization (WHO), met in July 2007 in attempt to plan the elimination of Chagas disease by 2010 (Chandy). Since cases have been identified in non-endemic countries such as the U.S, Canada and Europe, this organization decided a globalized effort would be best for the elimination of this disease. The WHO plans to take action in areas including Òstrengthening epidemiological surveillance and information systems, preventing transmission by blood transfusion and organ transplantation in endemic and non-endemic countries, identifying a diagnostic test(s) for screening and diagnosis of infections, explanding secondary prevention of congenital transmission and case management of congenital and non-congenital infections, and promoting a consensus on adequate case managementÓ (Chandy). The success of this groupÕs plan would be extremely positive.
Fortunately for our class, we are at low risk for contracting this disease since we will not be in disease-vulnerable situations. Even though the chances of someone in our group actually contracting this disease is slim, Chagas disease is still important to learn about because of its various effects on Costa Rica. My research has only described one disease, yet it is overwhelming to consider all of the other diseases affecting Costa Rica, and the sum of their effects. Costa Ricans should do what they can to take control of their disease situation. Like my past ecology teacher says, ÒAn ounce of prevention is worth a pound of cure.Ó
References:
"Chagas Disease." MDtravelhealth. 2007. 16 May 2008 Chandy, Babichan K. "WHO-Facts Sheet." Kuwait Medical Journal 3.39 (Sept. 2007): "Disease." Centers for Disease Control and Prevention. 15 Aug. 2007. 16 May 2008 Doyle, Patricia, PhD. "Hideous Chagas Disease Now Transmitted By Food." rense.com. Montenegro, Victor M, et al. "Chagas Disease in Dogs from Endemic Areas of Costa "Ortho-Clinical Diagnostics Receives FDA Approval for First Blood-Screening Test for Santenello, and Rehg. "The Case of a Tropical Disease and Its Treatment ." National Smith, Michael L. "The Kiss of Death." COCORI Complete Costa RIca. 1 Nov. 1998. 16 Teixeira, Antonio R.L., et al. "Emerging Chagas Disease: Trophic Network and Cycle of Vaz, V. C., P. S. D'Andrea, and A. M. Jansen. "Effects of habitat fragmentation on wild
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