Popular Media Piece

            Above is a 2014 Fox News segment about Chagas disease.  Like most things on the news, the video is overdramatized, superficial, and lacking crucial or even accurate information. 

            To start, reporters give off the impression that some new, terrifying disease is ravaging through America.  In reality, Chagas disease has been a problem for a long time, not to mention the fact that Chagas disease was a serious health issue decades ago before prevention programs were initiated by the World Health Organization and South American countries.

            The tagline and the comparisons made by the reporters greatly overdramatize the disease.  The tagline states “Researchers worry incurable disease is the ‘new AIDS of the Americas.’”  Chagas disease and AIDS have almost nothing in common apart form the fact that they both have asymptomatic phases and potentially fatal symptoms that occur later in life.  Based on those standards, a whole slew of diseases that have latent phases or no immediate symptoms are “the new AIDS.”  Prostate cancer fits that description better than Chagas does, with mortality rates and prevalence closer to that of AIDS than Chagas is.  Additionally, the pathology of the two diseases is completely different. AIDS is brought on by a virus, while Chagas is caused by parasites.  A large number of Chagas patients never experience symptoms, while AIDS commonly causes secondary complications.  The list goes on and on.

            The news clip did include an interview from a credible doctor, but most of the information came from a reporter.  The reporter doesn’t even give correct information.  He states that the disease is transmitted when a “blood sucking insect sends a parasite into your blood” through its bite.  This is not an accurate description of the transmission, as the parasites enter the host through wound contamination with feces.

            Instead of trying to scare people, the reporters should have mentioned how the morbidity rates in the U.S. are very low, the mortality rates are even lower, and that the disease is not easily passed from one person to another.  They mention how important it is to catch the infection fast, but they don’t mention the acute phase symptoms people should look for, or what population is most at risk.  Instead of talking about how prevention programs have greatly reduced incidence of the disease, they state that the disease is apparently “spreading at an alarming rate,” backing that up with no significant statistics.

            I never trust the news to give me accurate information, and this is just another example.

 Reference:

300,000 people in U.S. have Chagas disease as country unsure how to deal with growing threat. (2014, October 21). Fox Television Studios. Retrieved June 19, 2015, from http://www.fox10phoenix.com/story/26849138/2014/10/21/300000-people-in-us-have-chagas-disease-as-country-unsure-how-to-deal-with-growing-threat

Current Primary Literature

            It is well known that triatomine insects are the main vectors of the parasite T. cruzi, the pathogenic agent of Chagas disease.  Because these vectors are found primarily in tropical climates, the prevalence of Chagas disease is restricted mostly to Central and South America.  However, if another insect were able to serve as a vector for the parasites, the prevalence of the disease may extend beyond the tropical areas.  With the continuing rise of bedbugs as a public heath problem, Salazar et al. (2015) wanted to investigate if common bedbugs could serve as a vector for T. cruzi and facilitate the spread of Chagas disease, questions that could have grave implications.

            To do this, experimenters set up four experiments.  In the first, experimenters sought to determine if infected mammalian hosts could transfer T. cruzi to bed bugs.  They infected ten female mice with the parasites and allowed bedbugs to feed on the mice.  After 21 days, researchers extracted feces from the bedbugs and analyzed it microscopically for the presence of T. cruzi.  They found that a majority of the bedbugs contracted the parasites and released them through their feces.

From Salazar et al. (2015)

            In the second experiment, researchers sought to determine if bedbugs could transmit T. cruzi to a mammalian host.  To do this, researchers infected a group of mice with the parasites, allowed bedbugs to feed on those mice, allowing them to become infected, and then allowed those infected bugs to cohabitate with uninfected mice for 30 days.  Blood samples were taken from the mice every 6 days and examined for parasites.  Researchers found by the end of the 30-day period that 58% of mice exhibited parasitemia.

            In the third experiment, researchers attempted to determine the ease at which the parasites could be transmitted transcutaneously.  To do this, researcher shaved a portion to the fur from a group of mice, caused microtrauma to some via pricks with a tuberculin needle, and caused microtrauma to other via application of uninfected bedbugs, which would produce bite bounds.  Finally, researchers applied a solution containing infected feces to the trauma areas.  Blood analysis determined that 60% of the mice the received needle pricks developed parasitemia, and 20% of those with bite wounds developed parasitemia.

            In the fourth experiment, researchers analyzed the defecation patterns of bedbugs after a blood meal.   By developing an apparatus that simulated human skin and recording the bugs with a video camera, researchers were able to determine that 83% of the bugs that fed on the blood also defecated near the feeding site, suggesting a high probability of infected feces coming in contact with bite wounds, causing infection.

            Although the results found here seem conclusive, this experiment needs to be replicated many more times.  The number of mice used in each experiment was very low (at most 12) and results with so few trials lacks statistical power.  Additionally, many other factors should be controlled for, or analyzed separately.  Temperature, for example, may play a large role in the tendency, or ability of the bed bugs to bite the mice.  If temperature is a significant variable, experimental results may help narrow the geographical area where bed bugs could potentially become a significant epidemiological problem.

Reference:

Salazar, R., Castillo-Neyra, R., Tustin, A., Borrini-Mayori, K., Naquira, C., & Levy, M. (2015). Bed Bugs (Cimex lectularius) as Vectors of Trypanosoma cruzi. American Journal of Tropical Medicine and Hygiene, 331-335. doi:10.4269/ajtmh.14-0483

Transmission, Treatment, and Prevention

Transmission

            As previously stated, Chagas disease is a vector born illness.  The primary form of transmission is through triatomine insects, also knows as ‘kissing bugs’ because they bite the face of victims, or knows as ‘assassin bugs’ because they attack while the victim is sleeping.  These bugs are blood-sucking insects that are capable of carrying the pathogenic parasite, T. cruzi.  When one of   The feces either enters the host’s body through the bite wound, or later through the conjunctiva when the host accidently rubs the infectious feces off their face and into their eye (CDC, 2013).  This is how the parasite is introduced into a new host.  The same parasite-containing insect may then go and infect more hosts, or an uninfected insect may contract the parasite my biting another host and ingesting infected blood, starting the chain of infection.

these insects bites a victim and sucks their blood, they also leave behind feces containing the pathogenic parasite.

            Although vectors are the primary form of transmission, the parasites can be spread in several other ways.  For example, because the parasites multiply in the blood during the acute phase, any contact with the infected blood can be infectious.  This was a particular problem during blood transfusions or organ transplants before screening for the disease began in 2007 (Kirchhoff, 2014).  Passage of the disease can also occur from mother to infant during childbirth.

Treatment/Prevention

            Anyone can get Chagas disease, but prevalence is highest to parts of Central and South America where the triatomine insects live.  Those living in rural areas of tropical endemic countries are at the highest risk.  People in these locations often also have poor living conditions.  Mud walls and thatched roofs give the triatomine insects places to live where they can easily bite and infect new hosts (WHO, 2015).

            If the presence of T. cruzi is detected shortly after infection, treatment with antiparasitic medication can be effective.  Benznidazole and nifurtimox have been shown to be almost 100% effective in curing the disease in the acute phase (Kirchhoff, 2014).  If the disease progresses into the chronic phase however, treatment becomes more difficult as time goes on.  These medications can still be taken to prevent the progression of the disease and lessen the probability of life-threatening symptoms developing later in life, but the parasites will likely never be completely eradicated.

            Although Chagas disease can be difficult to detect and treat, great efforts have been made to reduce its prevalence and spread in endemic countries.  The main focus has been on vector control.  By spraying insecticides near homes and improving housing conditions, the triatomine insects can no longer live near potential human hosts.  People in these rural endemic areas have also been educated to look out for the triatomine insects and to sleep with bed nets to prevent potentially infectious bites.  Finally, spread of the disease from blood transfusions and organ transplants has been curbed by implementation of screening processes (WHO, 2015).

            There is no doubt that these preventative measures have been effective.  According to a recent epidemiological study, the implementation of a multi-country coordinated prevention program in South America has led to a 70% reduction in Chagas disease incidence (Moncayo & Silveira, 2009). 

From Moncayo & Silveira, 2009 

Although preventative measures are effective, the lack of a treatment for the disease is worrisome.  It could be argued that because the main populations at risk for the disease are poor populations, drug companies have little incentive to develop new, expensive treatments that can cure the chronic form of the disease.  While the WHO and individual countries have done well to educate the public and implement prevention programs, it may also be up to them to do the research and development necessary to find a cure.  Research shows that the prevention program in Brazil saves $17 in reduced healthcare and disability costs for every dollar spent on prevention (Moncayo & Silveira, 2009).  This money saved should be reinvested in research and development to help those that are actually dying from the disease.

References:

American Trypanosomiasis (also known as Chagas Disease). (2013). Centers for Disease Control and Prevention.  Retrieved June 18, 2015, from http://www.cdc.gov/parasites/chagas/.

Chagas disease (American trypanosomiasis). (2015). World Health     Organization. Retrieved June 18, 2015, from http://www.who.int/mediacentre/factsheets/fs340/en/.

Kirchhoff, L. (2014). Chagas Disease (American Trypanosomiasis).  Medscape. Retrieved June 18, 2015, from http://emedicine.medscape.com/article/214581-overview.

Moncayo, Á, & Silveira, A. (2009). Current epidemiological trends for Chagas disease in Latin America and future challenges in epidemiology, surveillance and health policy. Memórias Do Instituto Oswaldo Cruz, 17-30. doi:10.1590/S0074-02762009000900005

Disease history/statistics, etiology, and symptoms

            Chagas disease, also known as American Trypanosomiasis, is a parasitic disease caused by the parasite Trypanosoma cruzi.  Chagas disease occurs primarily in endemic regions of Latin America, but has spread to other places of the world, such as the U.S. and Europe.  It is estimated that 6 to 7 million people worldwide have the disease (WHO, 2015).  The parasite T. cruzi usually infects hosts through the vector triatominae, an insect also known as the ‘kissing bug’ because it commonly bites victims on or near their face.

An example of Romaña’s sign.

            Once the parasites have infected a host, they invade host cells and begin to multiply by binary fission (CDC, 2013).  At the end of this incubation period, infected cells burst, releasing more parasites into the bloodstream where they can travel to and infect other parts of the body.  This lytic phase and secondary infection characterize the acute phase of the disease.  The acute phase lasts for about two months after infection.  Often, the acute phase is asymptomatic, or only presents as generic cold symptoms such as fever, headache, swollen lymph nodes, etc.  This, in conjunction with the fact that this disease is most common in areas where access to healthcare is limited, makes it very difficult to detect and document cases of the disease (Kirchhoff, 2014).  One sign unique to the acute phase of Chagas disease is known as Romaña’s sign, which is the swelling of the eyelid caused by the entry of the parasite through the conjunctiva of the eye.

Life cycle of T. cruzi and the progression of Chagas disease

            Once the acute phase subsides, parasites are no longer found in high quantities in the blood.  Instead, they essentially lay dormant in tissues of the heart and digestive muscles.  This characterizes the chronic phase.  The prolonged asymptomatic form of infection is termed ‘chronic indeterminate.’ Many people go the remainder of their lives in the phase, never experiencing any symptoms (CDC, 2013).  However, 20-30% of infected people do experience symptoms later on in life, during the ‘chronic determinate’ phase.  Symptoms include cardiac disorders, such as arrhythmias that can result in sudden death.  Patients may also suffer from gastrointestinal problems, such as enlargement of the esophagus or colon causing difficulty swallowing and passing stool.  Additionally, a small percentage of patients suffer from neurological dysfunction that contributes to the severity of other previously mentioned symptoms (WHO, 2015).

            As mentioned previously, Chagas disease is often asymptomatic, making detection and diagnosis difficult.  If infection is suspected, blood samples can be analyzed in order to identify the presence of T. cruzi parasites.  Thick and thin blood smears are made and stained to help visualize the parasites.  Microscopic identification is only possible in the acute phase when parasites are circulating in the blood at high numbers.  If the patient is in the chronic phase, diagnosis can be accomplished through serological testing for specific antibodies to T. cruzi (Kirchhoff, 2014).

References:

American Trypanosomiasis (also known as Chagas Disease). (2013). Centers for Disease Control and Prevention.  Retrieved June 18, 2015, from http://www.cdc.gov/parasites/chagas/.

Chagas disease (American trypanosomiasis). (2015). World Health Organization. Retrieved June 18, 2015, from http://www.who.int/mediacentre/factsheets/fs340/en/.

Kirchhoff, L. (2014). Chagas Disease (American Trypanosomiasis).  Medscape. Retrieved June 18, 2015, from http://emedicine.medscape.com/article/214581-overview.