Elimination of Rhodnius prolixus in El Salvador, Central America

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Elimination of Rhodnius prolixus in El Salvador, Central America

Rafael Antonio CedillosI, ⁺; José Eduardo Romero^II; Emi Sasagawa^III

^IConsejo de Investigaciones Científicas, Universidad de El Salvador, San Salvador, El Salvador

^IIUnidad de Vigilancia de Enfermedades Vectorizadas, Ministerio de Salud, San Salvador, El Salvador

^IIIAgencia de Cooperación Internacional del Japón, San Salvador, El Salvador

ABSTRACT

Epidemiological studies performed in El Salvador between 1955-1972 demonstrated a high frequency of two triatomine vectors (Triatoma dimidiata and Rhodnius prolixus). However, the frequency of R. prolixus decreased by 1976 and this species has not been found since 1995. The main factors influencing the elimination of R. prolixus in El Salvador are discussed in this paper.

Key words:Rhodnius prolixus - elimination - El Salvador - Central America

Chagas disease has been known in Central America since 1913 when the first human case was reported in El Salvador (Segovia 1913), though El Salvador was the second country in Latin America to report cases of this disease after its discovery by Carlos Chagas in Brazil (Chagas 1909). Rhodnius prolixus (Stål, 1859) was first detected in El Salvador by a Brazilian investigator (Neiva 1915), apparently among specimens sent by Segovia for identification, and this vector most likely originated from Venezuela (Zeledón 1972, 2004, Dujardín et al. 1998, Schofield & Dujardín 1999). The insect is exclusively domestic and is well adapted to thatch and straw dwellings located at elevation below 800 m in El Salvador; thus, eliminating this type of housing can reduce the population size of this insect. In addition, R. prolixus is susceptible to the insecticides used in antimalarial programmes. The progressive reduction in the frequency of R. prolixus relative to the frequency of Triatoma dimidiata, the causative agent of Chagas disease, in El Salvador is shown in Table. The decrease is expressed by the mean number of triatomine insects collected during several studies performed between 1955-2010 (Peñalver et al. 1957, Cedillos et al. 1976, 2002, Romero et al. 2011).

The following are among the reasons for the elimination of R. prolixus in El Salvador: (i) the reduction in the percentage of straw huts, a natural habitat for this vector in this country, from 32.9% in 1971 to 0.5% in 2007, (ii) the use of insecticides for malaria control - houses that had been sprayed with DDT or propoxur up to 20 months before the survey in 1976 were found to be negative for triatomines, in comparison with an infestation rate of 50% reported in houses that were never subjected to insecticide treatment, (iii) the land reform in 1989, which favoured the building of adobe or brick houses in rural areas, and (iv) the remittances sent by Salvadoran immigrants from the United States of America and other countries around the world, estimated at one to three billion dollars annually since 1980, which allowed many families to improve the construction of their houses.

In 2008, Guatemala became the first country in Central America to be certified by the Initiative of the Countries of Central America for Control of Vector-Borne and Transfusional Transmission and Medical Care for Chagas Disease (IPCA) as having interrupted the transmission of Chagas disease by R. prolixus. In 2011, Honduras and Nicaragua were also in the process of eliminating the disease transmission due to this vector (Hashimoto & Schofield 2012). Despite the improvements regarding R. prolixus, the current situation for T. dimidiata, a native species found in all Central American countries in domestic, peridomestic habitats and even urban areas, presents a permanent challenge to the control strategy for Chagas disease in the area. The elimination of T. dimidiata is not feasible, but the reduction of domestic infestation is a viable target (Ponce 2007). In El Salvador, significant progress in controlling T. dimidiata is being achieved through a massive insecticide-spraying program with community participation and health promotion. This program resulted in a reduction in the percentage of infested houses from 60% in 2003 when the control program started to 40% in 2007 and 2.5% in 2011 in the areas under surveillance and control. The number of acute cases of Chagas disease in the country also declined from 117 cases in 2006 to 16 cases in 2010 (Romero et al. 2011).

The elimination of R. prolixus was validated by the XII Meeting of the Central American Initiative of Chagas Disease Control held in San Salvador in June 2010. At this meeting, El Salvador was formally declared free of Chagas disease transmission due to this vector.

Received 31 March 2012

Accepted 17 July 2012

• Cedillos RA, Francia H, Soundy-Call J, Ascencio G, Valcárcel-Novo M 2002. Estudio epidemiológico de la infección por Trypanosoma cruzi en El Salvador, Centro América. Available from: cic.ues.edu.sv/2/1/22-32.
• Cedillos RA, Warren McW, Jeffery GM, Wilton DP, Sauerbrey M 1976. Estudio epidemiológico de Trypanosoma cruzi en El Salvador, Centro América. Rev Inst Invest Med 5: 119-130.
• Chagas C 1909. Nova tripanozomiaze humana: estudos sobre a morfolojia e o ciclo evolutivo do Schizotrypanum cruzi n. gen., n. sp., ajente etiolojico de nova entidade morbida do homem. Mem Inst Oswaldo Cruz 1: 159-218.
• Dujardín JP, Muñoz M, Chávez T, Ponce C, Moreno J, Schofield CJ 1998. The origin of Rhodnius prolixus in Central America. Med Vet Entomol 12: 113-115.
• Hashimoto K, Schofield CJ 2012. Elimination of Rhodnius prolixus in Central America. Parasit Vectors 5: 45.
• Neiva A 1915. Contribuição para o conhecimento dos hemípteros hematófagos da América Central. Brasil Med 29: 1-3.
• Peñalver JM, Rodríguez MI, Bloch M, Sancho G 1957. Tripanosomiasis en El Salvador. Arch Col Med El Salv 10: 1-21.
• Ponce C 2007. Current situation of Chagas disease in Central America. Mem Inst Oswaldo Cruz 102 (Suppl. I): 41-44.
• Romero Chévez JE, Ramos HR, Sasagawa E 2011. Avances hacia la interrupción de la transmisión de la enfermedad de Chagas en El Salvador 2003-2010, OPS/OMS, MINSAL JICA, UES, El Salvador, 64 pp.
• Schofield CJ, Dujardín JP 1999. Theories in the evolution of Rhodnius prolixus Actualid Biol Medellín 21: 183-197.
• Segovia JC 1913. Un caso de tripanosomiasis. Archivos Hospital Rosales (San Salvador) 8: 249-254.
• Zeledón R 1972. Los vectores de la enfermedad de Chagas en América. In Simposio Internacional sobre Enfermedad de Chagas, Sociedad Argentina de Parasitología, Buenos Aires, p. 327-345.
• Zeledón R 2004. Some historical facts and recent issues related to the presence of Rhodnius prolixus (Stål 1859) (Hemiptera: Reduviidae) in Central America. Entomol Vect 4: 233-246.

Publication Dates

• Publication in this collection
  03 Jan 2013
• Date of issue
  Dec 2012

History

• Received
  31 Mar 2012
• Accepted
  17 July 2012