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Foley J, López-Pérez AM, Rubino F, Backus L, Ferradas C, Barrón-Rodriguez J, Mendoza H, Arroyo-Machado R, Inustroza-Sánchez LC, Zazueta OE. Roaming Dogs, Intense Brown Dog Tick Infestation, and Emerging Rocky Mountain Spotted Fever in Tijuana, México. Am J Trop Med Hyg 2024; 110:779-794. [PMID: 38377609 PMCID: PMC10993825 DOI: 10.4269/ajtmh.23-0410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 10/30/2023] [Indexed: 02/22/2024] Open
Abstract
A two decades-long epidemic of Rocky Mountain spotted fever in northern México reached the U.S. border city of Tijuana in 2021. Cases were near the city periphery in marginalized areas, some lacking infrastructure such as streets or utilities. We worked in the three census areas where human cases were reported and in 12 additional control Áreas Geoestadisticas Básicas. There were dogs, the primary tick host and Rickettsia rickettsii reservoir, in 76% of homes, with 2.2 owned dogs per home on average, approximately equal numbers of roaming dogs were seen, and 46.2% of owned dogs were allowed to roam in the street. Sixty-eight percent of people had heard of Rocky Mountain spotted fever (RMSF), and 35% self-reported tick infestation, including 19% of homes without dogs. Ticks appeared to move among houses of adjacent neighbors. Of 191 examined dogs, 61.8% were tick-infested, with 6-fold increased odds if they were allowed to roam. Although no dogs were Rickettsia polymerase chain reaction-positive, we found one R. rickettsii- and 11 Rickettsia massiliae-infected ticks. The rickettsial IgG seroprevalence by immunofluorescence antibody assay was 76.4%, associated with unhealthy body condition, adults, dogs with >10 ticks, more dogs being seen in the area, and dogs being permitted in the street. Insufficient medical and canine management resources have contributed to a case fatality rate of RMSF that has exceeded 50% in areas. High canine seroprevalence suggests risks to people and dogs; unfortunately, herd immunity is impeded by high turnover in the canine population owing to the birth of puppies and high death rates. Binational One Health workers should monitor disease spread, enact canine population management and tick eradication, and provide prevention, diagnostic, and treatment support.
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Affiliation(s)
- Janet Foley
- School of Veterinary Medicine, University of California, Davis, California
| | - Andrés M. López-Pérez
- School of Veterinary Medicine, University of California, Davis, California
- Red de Biología y Conservación de Vertebrados, Instituto de Ecología, Xalapa, México
| | - Francesca Rubino
- School of Veterinary Medicine, University of California, Davis, California
| | - Laura Backus
- School of Veterinary Medicine, University of California, Davis, California
| | - Cusi Ferradas
- School of Veterinary Medicine, University of California, Davis, California
- Emerge, Unidad de Investigación en Enfermedades Emergentes y Cambio Climático, Universidad Peruana Cayetano Heredia, Lima, Perú
| | - Julio Barrón-Rodriguez
- Departamento de Ecología, Fauna Silvestre y Animales de Laboratorio, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, México City, México
| | - Hugo Mendoza
- Departamento de Ecología, Fauna Silvestre y Animales de Laboratorio, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, México City, México
| | | | | | - Oscar E. Zazueta
- Departamento de Epidemiología, Secretaría de Salud de Baja California, Mexicali, México
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Zazueta OE, Armstrong PA, Márquez-Elguea A, Hernández Milán NS, Peterson AE, Ovalle-Marroquín DF, Fierro M, Arroyo-Machado R, Rodriguez-Lomeli M, Trejo-Dozal G, Paddock CD. Rocky Mountain Spotted Fever in a Large Metropolitan Center, Mexico-United States Border, 2009-2019. Emerg Infect Dis 2021; 27. [PMID: 34014151 PMCID: PMC8153879 DOI: 10.3201/eid2706.191662] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Longevity, high prevalence, and multifocal distribution of this disease pose unprecedented public health challenges. Epidemic levels of Rocky Mountain spotted fever (RMSF) have persisted in Mexicali, Mexico, since the initial outbreak was first reported in December 2008. We compared clinical and epidemiologic data of cases in Mexicali during 2009–2019 between patients with an IgG titer reactive with Rickettsia rickettsii bacteria by indirect immunofluorescence antibody (IFA) assay and those who demonstrated DNA of R. rickettsii in a whole blood sample when tested by PCR. We identified 4,290 patients with clinical and epidemiologic features compatible with RMSF; of these, 9.74% tested positive by IFA and 8.41% by PCR. Overall, 140 patients died (11-year case-fatality rate 17.97%). Substantial differences in the frequency of commonly recognized clinical characteristics of RMSF were identified between PCR-positive and IFA-positive cases. The Mexicali epidemic is unique in its size and urban centralization. Cases confirmed by PCR most accurately reflect the clinical profile of RMSF.
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