Human ehrlichiosis are emerging tick-borne infections that were first recognized in humans in 1987.1 Human infections are caused by at least 3 distinct species: Ehrlichia chaffeensis, E. ewingii, and Anaplasma phagocytophilum.2 Ehrlicihia chaffeensis and A. phagocytophilum are the causative agents of human monocytic ehrlichiosis (HME) and human granulocytic anaplasmosis (HGA), respectively. Serosurveys and molecular techniques have documented the presence of human ehrlichiosis in South America.3–7 Evidence of human ehrlichiosis in Peru is lacking although E. canis infection was recently demonstrated in dogs.8 Given the absence of data, we conducted a serosurvey in geographically distinct rural communities from Peru to establish the possible presence of this pathogen.
Healthy inhabitants from four communities were surveyed for the presence of antibodies against E. chaffeensis and A. phagocytophilum (Figure 1).
The first community was Cura Mori (population = 159), a sea level rural community located in the northern coastal region of Peru 15 km southwest of Piura. Agriculture and animal husbandry (e.g., swine, goats) are the main economic activities of the community. Village inhabitants live in adobe houses with no piped water or sewage systems.
The second community was Cochapata (population = 138), a rural village in the southern Peruvian Andes situated 98 km north of Cuzco at an altitude of 4,173 meters. The main sources of employment are agriculture and animal husbandry. Livestock raised by the community include swine, sheep, and cattle. Village inhabitants live in adobe houses with dirt floors and piped river water. Serum samples in Cura Mori and Cochapata were obtained as part of a cysticercosis serosurvey during 1999.
The third community was Santo Tomas (population = 1,293), a rural community on the Nanay River in the northeastern Amazon in Peru. The town is located 15 km from Iquitos. Agriculture is the main economic activity. Most of the population relies on wells for drinking water and uses latrines for waste disposal. Houses are generally made of wood, and some are without walls, with palm leaf roofs usually open at the top.
The fourth community was Pampas, a sea level, peri-urban shantytown (population = 40,000) located in the southern part of Lima. It is located near the Pacific Ocean and has a desert climate. Households are built next to each other and made of woven thatch walls with roofs of plastic coverings, usually containing one or two bedrooms. Most houses in this area have piped water. Serum samples in Santo Tomas and Pampas were collected as part of surveys of strongyloidiasis during 1998 and 2003 respectively.
This study was reviewed and approved by the ethical review boards of AB Prisma (Lima, Peru) and the Johns Hopkins University School of Public Health (Baltimore, Maryland). Serologic specimens were tested in a private laboratory for immunoglobulin G antibodies against E. chaffeensis (HME) and A. phagocytophilum (HGA) by indirect immunofluorescence assay (IFA). The HGA and HME IFAs were performed on all the serum samples according to the manufacturer’s instructions (IGeneX Inc, Palo Alto, CA). Titers ≥ 80 were considered positive.
Mean age of participants whose age was available (n = 78) was 30.2 years (range = 6–85 years). An overall seroprevalence for HME of 13% (21 of 160) was found by IFA. Five (95) of 53 were males and 16 (15%) of 106 were females. Seroprevalences of 25% (10 of 40), 23% (9 of 40), 3% (1 of 40), and 3% (1 of 40) were found in Cura Mori, Cochapata, Pampas, and Santo Tomas, respectively. Seroprevalences in Cura Mori and Cochapata were significantly higher than in Pampas and Santo Tomas (P < 0.01, by chi-square test). Twelve persons (8%) had titers ≥ 160. All HGA IFA test results were negative.
Our findings suggest that antibodies against E. chaffeensis or other closely related Ehrlichia spp. are present in human serum samples from geographically distinct communities in Peru. No sera were reactive to A. phagocytophilum.
Human ehrlichiosis was first reported in Venezuela where polymerase chain reaction (PCR) techniques demonstrated that up to 30% of patients with HME could be infected with E. canis.9 Use of similar techniques in a more recent study suggested an E. chaffeensis infection in a Venezuelan child.7 Serosurveys in Argentina, Brazil, Chile, Mexico, and Venezuela have detected human ehrlichiosis3–6,10 but it is unclear what Ehrlichia species may be causing human infection. Recent findings using molecular diagnostic techniques indicate that E. chaffeensis may be present in the Brazilian marsh deer, which suggests that this mammal may act as a natural reservoir of the agents that cause HME. 11 High seroprevalences of ehrlichiosis observed in the rural communities of Cura Mori and Cochapata may be caused by vertebrate reservoirs that remain to be identified. Livestock and dogs are quite prevalent in these communities and their role as potential reservoirs of the bacterium should be explored.
In North America, E. chaffeensis is transmitted by the lone star tick, Amblyomma americanum, but this tick is not present in South America. Amblyomma cajennense is known to transmit rickettsial spotted fever in South America and has been implicated as the possible vector of E. chaffeensis.4 Further studies using molecular techniques are needed to clarify if this tick may be involved in the transmission of E. chaffeensis if this organism indeed occurs in South America.
In our study, we used E. chaffeensis and A. phagocytophilum antigen in the IFA and did not test sera against other ehrlichial species. Serologic cross-reactions between E. chaffeensis, E. ewingii, E. canis, and Rickettsia rickettsii are known to occur. 12 Therefore, we cannot exclude the possibility that cross-reacting antibodies may have been detected in some persons. In our experience, sera containing R. rickettsii cross-reacting antibody give false-positive reactions in HME and HGA IFAs. We did not find any serum samples positive in both assays; therefore, it is unlikely that cross-reactions with this organism occurred. It is important to rule out cross-reactivity with R. rickettsii because serologic evidence of human infection with this pathogen has been demonstrated near the study communities of Cura Mori and Cochapata. 13
Our findings and the recent description of a new strain of E. canis identified in Peruvian dogs using PCR techniques highlight the importance of ehrlichiosis as an emerging infection in Peru. There is a need for deliberate search of human cases in Peru, especially among patients with compromised immunity such as infection with human immunodeficiency virus in whom severe or fatal HME has been described. 12 Further studies are needed to characterize the Ehrlichia species in Peru and the natural reservoirs and tick vectors involved in transmission and their clinical significance.
Map of Peru showing locations of study sites.
Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 80, 2; 10.4269/ajtmh.2009.80.242
Map of Peru showing locations of study sites.
Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 80, 2; 10.4269/ajtmh.2009.80.242
Map of Peru showing locations of study sites.
Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 80, 2; 10.4269/ajtmh.2009.80.242
Address correspondence to Manuel H. Moro, Division of Comparative Medicine, National Center for Research Resources, National Institutes of Health, 6701 Democracy Boulevard, Bethesda, MD 20892. E-mail: manuel.moro@nih.gov
Authors’ addresses: Pedro L. Moro, Immunization Safety Office, Office of the Chief Science Officer, Centers for Disease Control and Prevention, 1600 Clifton Road, Mailstop D26, Atlanta, GA 30333, E-mail: pmoro@cdc.gov. Jyotsna Shah, and Nick Harris, IGeneX Inc., 797 San Antonio Road, Palo Alto, CA 94303, E-mails: jyotsna@aol.com and nharris@aol.com. Olga Li, Laboratorio de Patología Clínica, Facultad de Medicina Veterinaria, Universidad Nacional Mayor de San Marcos, Lima, Peru, E-mail: Olgalie@hotmail.com. Robert H. Gilman, Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Room W5515, Baltimore, MD 21205, E-mail: rgilman@jhsph.edu. Manuel H. Moro, Division of Comparative Medicine, National Center for Research Resources, National Institutes of Health, 6701 Democracy Boulevard, Bethesda, MD 20892, E-mail: manuel.moro@nih.gov.
Acknowledgments: We thank Dr. Sergio Recuenco (Centers for Disease Control and Prevention, Atlanta, GA) Dr. Ofelia Zegarra-Moro from (Kansas State University, Manhattan, KS), and Lilia Cabrera (A.B. Prisma, Lima, Peru) for useful advice.
Disclosure: The authors report no conflicts of interest with the study.
REFERENCES
- 1↑
Maeda K, Markowitz N, Hawley RC, Ristic M, Cox D, McDade JE, 1987. Human infection with Ehrlichia canis, a leukocytic Rickettsia.N Engl J Med 316 :853–856.
- 2↑
Dumler JS, Madigan J, Pusteria N, Bakken J, 2007. Ehrlichiosis in humans: epidemiology, clinical presentation, diagnosis, and treatment. Clin Infect Dis 45 :S45–S51.
- 3↑
Calic S, Galvao M, Bacellar F, Rocha C, Mafra C, Leite R, Walker D, 2004. Human ehrlichiosis in Brazil: first suspect cases. Braz J Infect Dis 8 :259–262.
- 4↑
Ripoll CM, Remondegui CE, Ordonez G, Arazamendi R, Fusaro H, Hyman MJ, Paddock CD, Zaki SR, Olson JG, Santos-Buch CA, 1999. Evidence of rickettsial spotted fever and ehrlichial infections in a subtropical territory of Jujuy, Argentina. Am J Trop Med Hyg 61 :350–354.
- 5
Lopez J, Rivera M, Concha JC, Gatica S, Loeffeholz M, Barriga O, 2003. Ehrlichiosis humana en Chile: evidencia serológica. Rev Med Chil 131 :67–70.
- 6↑
Perez M, Rikihisa Y, Wen B, 1996. Ehrlichia canis-like agent isolated from a man in Venezuela: antigenic and genetic characterization. J Clin Microbiol 34 :2133–2139.
- 7↑
Martínez MC, Gutiérrez CN, Monger F, Ruiz J, Watts A, Mijares VM, Rojas MG, Triana-Alonso FJ, 2008. Ehrlichia chaffeensis in child, Venezuela. Emerg Infect Dis 14 :519–520.
- 8↑
Vinasco J, Li O, Alvarado A, Diaz D, Hoyos L, Tabachi L, Sirigireddy K, Ferguson C, Moro MH, 2007. Molecular evidence of a new strain of Ehrlichia canis from South America. J Clin Microbiol 45 :2716–2719.
- 9↑
Perez M, Bodor M, Zhang C, Xiong Q, Rikihisa Y, 2006. Human infection with Ehrlichia canis accompanied by clinical signs in Venezuela. Ann N Y Acad Sci 1078 :110–117.
- 10↑
Gongóra-Biachi RA, Zavala-Velázquez J, Castro-Sansores CJ, González-Martínez P, 1999. First case of human ehrlichiosis in Mexico. Emerg Infect Dis 5 :481.
- 11↑
Machado RZ, Duarte JM, Dagnone AS, Szabó MP, 2006. Detection of Ehrlichia chaffeensis in Brazilian marsh deer (Blastocerus dichotomus). Vet Parasitol 30 :262–266.
- 12↑
Paddock CD, Childs JE, 2003. Ehrlichia chaffeensis: a prototypical emerging pathogen. Clin Microbiol Rev 16 :37–64.
- 13↑
Schoeler GB, Morón C, Richards A, Blair PJ, Olson JG, 2005. Human spotted fever rickettsial infections. Emerg Infect Dis 11 :622–624.