Household Infestation Rates of Chagas Disease Vectors and Trypanosoma cruzi Prevalence in Southern EcuadorStanton Jasicki • Dr. Daniel Herman • Dr. Mario Grijalva • Sofía Ocaña

Introduction

Chagas disease affects an estimated 10 million people across its endemic regions in Central and South America (WHO, 2010). The disease is caused by the parasite Trypanosoma cruzi, and presents itself in two stages. The acute stage is marked by flu-like symptoms such as fever, headaches, and muscle pain. The chronic stage is when classic cardiac, digestive, and neurological disorders are observed.

The most common vectors for transmission of T. cruzi, and thus Chagas disease, are members of the Triatominae subfamily. These beetles, collectively referred to as triatomines or commonly as kissing bugs, feed on vertebrate blood. Transmission of T. cruzi usually occurs when a triatomine bites an exposed area of skin and then defecates. The natural instinct to scratch a bite is all that is needed to allow the parasite present in the fecal matter to enter the body.

Household rates of infestation are unknown in many rural areas of Chagas disease’s endemic areas. The purpose of this study was to detect the presence of triatomines within 13 rural communities of Loja Province in Ecuador as well as to determine the seropositivity for T. cruzi of residents within the communities.

Methods

Houses in each of the 13 communities were screened for the presence of triatomines. Screenings consisted of 2 individuals thoroughly examining the house and surroundings (chicken nests, woodpiles, bathrooms, etc.) for 30 minutes. If live triatomines were found, the home was considered infested. A total of 354 houses were searched.

Screening for T. cruzi within the 13 communities was accomplished with the use of InBios and Stat-Pak rapid field tests, both of which are specific to antibodies produced to T. cruzi. Individuals whose blood reacted positively for either of the field tests were subjected to a second round of the same field tests. They were also were asked to give a blood sample so their serum could be tested with the same field tests for further confirmation

Results

CommunityFirst

Stat-PakSecond Stat-Pak

Stat-Pak Serum

First InBios

Second InBios

InBios Serum

Jurupe Positive Positive Positive Negative Negative NegativeTuburo Positive Positive Positive Negative Negative NegativeTuburo Negative Negative Negative Positive Positive NegativeTuburo Positive Positive Positive Negative Negative NegativeTuburo Negative Negative Negative Positive Positive NegativeTundurama Positive Positive Negative Negative Negative NegativeSanta Ester Positive Negative Positive Negative Negative Negative

Conclusions

• Of the 354 houses searched, 48 houses were found to be infested.

• Across the 13 communities, infestation indices ranged from 0- 32.1%, with an average infestation index of 13.56%.

• The highest infestation indices were seen in Tacoranga (32.1%), Coamine (25.0%), Jurupe (25.0%), Guara (24.0%), Chirimoyos (16.7%), and Chaquizhca (15.2%).

• Infestations were not observed in Galapagos and El Tingo.

• Of the total 949 individuals screened for Chagas disease using the rapid field tests, 7 positive results were obtained, corresponding to a prevalence of 0.74%.

• Positive field tests were obtained in Santa Ester, Jurupe, Tuburo, and Tundurama, with 4 out of 7 positive individuals residing in Tuburo.

• Reactive Stat-Pak field tests yielded negative results for InBios tests. Likewise, individuals who tested positive, using InBios, tested negative when using Stat-Pak.

Left: Positive field tests. Right: Performing field tests.

Table 2: Number of positive results obtained and prevalence by community and county.

Table 3: Results from first, second and serum based field tests, as well as the community they were obtained from.

Community County Individuals screened

Positive results

Prevalence (%)

Ashimingo Paltas 66 0 0 Coamine Paltas 87 0 0 Tacoranga Paltas 65 0 0 Santa Ester Gonzanamá 43 1 2.33 Chirimoyos Gonzanamá 11 0 0 Jurupe Gonzanamá 48 1 2.08 Galapagos Quilanga 65 0 0 Tuburo Quilanga 55 4 7.27 Guara Calvas 66 0 0 Chaquizcha Calvas 142 0 0 Machay Espíndola 55 0 0 Tundurama Espíndola 129 1 0.78 El Tingo Espíndola 117 0 0

Totals 949 7 0.74

Communities County Houses

searched Infested houses

Infestation index (%)

Ashimingo Paltas 20 1 5 Coamine Paltas 40 10 25 Tacoranga Paltas 28 9 32.1 Santa Ester Gonzanamá 16 1 6.3 Chirimoyos Gonzanamá 6 1 16.7 Jurupe Gonzanamá 28 7 25 Galapagos Quilanga 28 0 0 Tuburo Quilanga 30 2 6.7 Guara Calvas 25 6 24 Chaquizcha Calvas 33 5 15.2 Machay Espíndola 26 1 3.8 Tundurama Espíndola 54 5 9.3 El Tingo Espíndola 20 0 0

Totals 354 48 13.56

Table 1: Total number houses searched and number of infested houses by community and county. Infestation indices are also given for each community.

Left: Trypanosoma cruzi life-cycle.

Right: Triatomine.

Acknowledgments

Special thanks to Dr. Daniel Herman, Dr. Mario Grijalva, Sofía Ocaña, and the Tropical Disease Institute of Ohio University.

Also, thanks to the Office of Research and Sponsored Programs for providing funding.

References

Centers for Disease Control and Prevention. (2009). Trypanosomiasis, American. Retrieved October 17, 2010, from http://www.dpd.cdc.gov/dpdx/HTML/TrypanosomiasisAmerican.htm.

World Health Organization. (2010). Chagas disease (American trypanosomiasis). Retrieved October 15, 2010, from http://www.who.int/mediacentre/factsheets/fs340/en/index.html.