The Unpleasant Kiss – Chagas Disease
The Unpleasant Kiss – Chagas’ Disease
In Memory of Keeper owned by Shari Herbet
by Jennifer Parks
Chagas’ (SHA-gus) disease is caused by infection with a protozoa of the genus Trypanosoma, which affect all domestic animals. The disease originated in Central and South America where it was first documented by Brazilian physician Carlos Chagas in 1909. It has since migrated to the United States along with immigrants from those countries. It is estimated that Eighteen million people are currently infected world wide, with up to 100 million at risk, and over a 1,000 documented cases here in the United States. It is caused by Trypanosoma cruzi (tri-PAN-o-so-MA cruise-EYE) and is characterized—in its chronic stage—by extensive myocarditis, cardiac arrhythmia, and ultimately death. The parasite multiplies inside cells, particularly of heart and smooth muscle. Dogs are mostly infected by blood-sucking insects, such as Triatoma infestans, also known as the kissing bug or assassin bug.
Animals can get Chagas’ disease by living or sleeping outside in an area where the “kissing bug” lives. This bug lives in cracks and holes of old, unkept buildings or homes and wooded areas. The protozoa develops in the intestine of the “kissing bug”. This bug is a blood feeder and will bite its host (animal or human), then excrete feces after feeding. This fecal material contains the protozoa, which then enters the bite wound created by the “kissing bug”.
What animals get Chagas’ disease?
In the U.S. dogs, opossums and armadillos are most likely to carry the protozoan that causes Chagas’ disease. Many other animals can serve as carriers, including cats, rabbits, raccoons, and rodents. Generally, dogs are the only animals that show signs of disease.
How does Chagas’ disease affect my animal?
In dogs, the most common signs of infection are fever, sluggishness and an unkept hair-coat. Signs of heart failure may show up after an extended period of time. Other animals do not typically show any signs of illness. Affected dogs may die suddenly or have long- or short-term inflammation of the heart muscle. Two clinical forms of the disease are recognized, acute and chronic. During the acute stage pathological damage is related to the presence of the parasite, whereas in the chronic stage few parasites are found.
Diagnosis of American Trypanosomiasis
In most areas where Chaga’s disease is present, the diagnosis of T. cruzi infection in humans or domestic animals relies on ELISA and IFAT tests. The diagnosis and treatment of this infection are active areas of investigation. New serological and molecular biological techniques have improved the diagnosis of chronic infection.
Treatment and Prevention Options
Therapy of Chaga’s disease with antitrypanosome therapy is most successful in the acute stage. Two medications are available: nifurtimox and benznidazole. Therapy is usually extended for a period of months, and cure rates are somewhat disappointing. Both medications carry a long list of significant side effects.
Current therapy for Chaga’s disease is not always effective and is limited by frequent and severe side effects. In one study, the effect of deltamethrin-treated dog collars (DTDCs) were evaluated over time on the population dynamics of Triatoma infestans, a main T. cruzi insect that transmits the protozoan infection. Bugs exposed to dogs wearing those collars became extinct 77–196 days after study initiation. Even a single exposure of bugs to dogs wearing deltamethrin-treated dog collars (DTDCs) significantly reduced feeding success of triatomine bugs. Thus, DTDCs could represent a novel tool to prevent and control canine and (hence) human Chaga’s disease. Tested collars could not only be a potential tool to prevent Chaga’s disease in endemic areas of human disease but also in areas where human disease is scarce and Chaga’s disease is mainly of veterinary importance (e.g., in the United States, where canine T. cruzi infections are regularly reported. Deltamethrin-treated collars have also been shown to protect dogs from sand flies and zoonotic .
Deltamethrin is a comparatively safe insecticide, with reportedly few systemic side effects that are usually reversible (e.g., neuroexcitation, gastroenteritis). It is heavily used in agriculture and public health to control crop pests or insect vectors of disease, and the consensus is that the gain in reduction of disease morbidity and mortality caused by its use outweigh the potential adverse events experienced by people exposed to it. As with any potentially toxic product, care should be taken to minimize required contact (e.g., not letting young children play with the collar, touch it, or put it in their mouth).
References:
1. Extinction of experimental Triatoma infestans populations following continuous exposure to dogs wearing deltamethrin-treated collars by R. Reitinger, L. Ceballos, R. Stariolo, C. R. Davies, and R. E. Gurtler 2. Fungal and Parasitic Infections of the Eye by Stephen A. Klotz, Christopher C. Penn, Gerald J. Negvesky, and Salim I. Butrus
Chagas’ Facts:
- Chagas Disease affects approximately 20 million worldwide, killing 50,000 each year, yet is practically unknown to most in the general public in the US.
- More than 100,000 Latin American immigrants living in the United States are chronically infected and a potential source of transmission of the disease by means of blood transfusions
- Infected triatomine bugs, that transmit T.cruzi, are found in North, Central and South America. Blood banks in selected cities of the continent vary between 3.0 and 53.0% -making the prevalence of T. cruzi infected blood higher than that of Hepatitis B, C, and HIV infection
- Numerous acute and chronic cases of the disease have been reported in domestic dogs in Texas, Oklahoma, Louisiana, South Carolina and Virginia
- In Texas infection rates in kissing bugs are reported to be 17-48%, in other states infection rates may not be known due to lack of knowledge about the disease and inadequate studies with regards to sampling bugs for the disease.
