Cat infected by a variant of bat rabies virus in a 29-year disease-free urban area of southern Brazil

Abstract

INTRODUCTION: After 29 years, rabies was detected in a cat in Curitiba, southern Brazil. METHODS: The fluorescent antibody test (FAT) and mouse inoculation test (MIT) were performed on central nervous system (CNS) samples. RESULTS: Direct immunofluorescence was negative, but the biological test was positive and rabies virus was characterized as variant 4 (from Tadarida brasiliensis). CONCLUSIONS: Reappearance of rabies in domestic animals warns of sylvatic-aerial risk of infection and the necessity of monitoring bats in historically rabies-free areas. [PUBLICATION ABSTRACT]

COMMUNICATION COMUNICAÇÃO

Cat infected by a variant of bat rabies virus in a 29-year disease-free urban area of southern Brazil

Gato infectado por variante do vírus rábico de morcego em uma área urbana do sul do Brasil há 29 anos livre da doença

Vivien Midori MorikawaI,II; Juliano RibeiroII; Alexander Welker BiondoI; Anaclete FelliniIII; Daniele BierI; Marcelo Beltrão MolentoI

ILaboratório de Doenças Parasitárias, Departamento de Medicina Veterinária, Universidade Federal do Paraná, Curitiba, PR

IICentro de Controle Zoonoses, Secretaria Municipal de Saúde, Curitiba, PR

IIILaboratório Central do Estado, Secretaria de Saúde do Estado do Paraná, São José dos Pinhais, PR

Address to

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ABSTRACT

INTRODUCTION: After 29 years, rabies was detected in a cat in Curitiba, southern Brazil.

METHODS: The fluorescent antibody test (FAT) and mouse inoculation test (MIT) were performed on central nervous system (CNS) samples.

RESULTS: Direct immunofluorescence was negative, but the biological test was positive and rabies virus was characterized as variant 4 (from Tadarida brasiliensis).

CONCLUSIONS: Reappearance of rabies in domestic animals warns of sylvatic-aerial risk of infection and the necessity of monitoring bats in historically rabies-free areas.

Keywords: Feline rabies. Nonhematophagous bat. Epidemiological surveillance.

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RESUMO

INTRODUÇÃO: Após 29 anos, raiva em um gato foi detectada em Curitiba, sul do Brasil.

MÉTODOS: Foram realizados imunofluorescência direta e prova biológica através de inoculação em camundongos para o diagnóstico da raiva.

RESULTADOS: A imunofluorescência direta foi negativa, mas a prova biológica foi positiva e o vírus caracterizado como variante 4 (de morcegos não hematófagos).

CONCLUSÕES: O reaparecimento da raiva alerta para o risco aéreo-silvestre de infecção e para a necessidade de monitoramento de morcegos em áreas historicamente livres da raiva.

Palavras-chaves: Raiva felina. Morcegos não-hematófagos. Vigilância epidemiológica.

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All mammals are susceptible to rabies and transmission in tropical countries involves two major cycles: the urban cycle, in which dogs and cats are the main sources of infection, and the sylvatic, where transmission mainly occurs from bats, monkeys and foxes1,2. Mass vaccination campaigns in dogs and cats have strongly reduced rabies throughout Brazil3. Meanwhile, cases of rabies transmitted by bats have increased in urban areas as a consequence of the environmental impact of urbanization on bat habitats, the shelter offered by man-made constructions and food from imbalanced urban fauna4.Not surprisingly, animal causes of infection in Latin America have switched since 2004 from dogs to bats2. The last two cases of human rabies in the State of Paraná, southern Brazil were registered in 1987, with a hematophagous bat (Desmodus rotundus) as agent, and in 1975, by a dog in Curitiba5. The last canine rabies infection in Curitiba was registered in 1981. Due to rabies control, no current massive rabies vaccination is in effect in Curitiba and the surrounding areas6. However, nonhematophagous bats positive for rabies have been recorded annually in recent years (Table 1). The present study reports the first case of cat rabies in Curitiba and surrounding areas for the past 29 years.

Curitiba (25º25'47 "S, 49º16'19" W) is the capital of the State of Paraná, southern Brazil, with an estimated population of 1,851,215 inhabitants, the seventh most populated city in Brazil7.On April 20th 2010, the Zoonoses Control Center (CCZV) was informed that a 3-year-old male cat not vaccinated against rabies had suddenly had a convulsion and died. Another 8 cats with free-access to the street and 2 dogs lived in the same household. These animals presented no clinical signs compatible with rabies and were vaccinated. The owner had tried to medicate the cat, during which she was bitten on the hand. Despite no definitive diagnosis at the time, the woman was submitted to the standard postinfection protocol for high rabies risk, anti-serum therapy and five doses of cell culture anti-rabies vaccine on days 0, 3, 7, 14 and 28, by the local primary healthcare clinic.

Central nervous system tissue from the cat was sent to the Paraná State Central Reference Laboratory (LACEN-PR), where fluorescent antibody test (FAT)8 using a panel of monoclonal antibodies proved to be negative. However, the Biological Test by intracerebral inoculation in mice9 was positive on day 17 out of a total of 21 days, indicating a viral strain with a prolonged incubation period. The owner was notified and local health authorities monitored the complete vaccination protocol and clinical status of the patient. Based on a monoclonal antibody panel, the virus isolated was characterized at the Pasteur Institute of Sao Paulo as variant 4, compatible with isolates from insectivorous bat Tadarida brasiliensis10.

Massive house to house vaccination was immediately initiated by the CCZV in a 1km diameter, such that a total of 874 dogs and 49 cats were vaccinated. Even though the source of cat infection was not identified, a nonhematophagous bat was probably the source of infection, which may currently represent the most dangerous species for human rabies infection. In 2009 and during the first four months of 2010, the Ministry of Health reported a total of 16 and 13 hematophagous and 165 and 114 nonhematophagous bats positive for rabies, respectively11. Although anti-vampire paste and mass capture/euthanasia have been reported as efficient at controlling the spread of hematophagous bat rabies3, these strategies applied to nonhematophagous bats may lead to species extinction; moreover, nonhematophagous bats are protected by the Brazilian Environmental Laws12. The recent capture, euthanasia and brain DIF testing of 200 T. brasiliensis bats in Curitiba in 2009 due to a rabies positive bat in a nearby colony resulted in all negative results, showing that geographical proximity may not indicate the source of infection6.A recent study has shown that commercial inactivated rabies vaccine immunoprotected the bat T. brasiliensis for over a year, suggesting that massive bat vaccination may be an alternative prevention program10. Regardless, active surveillance for rabies involving continuous monitoring of such populations should be conducted in urban areas of large Brazilian cities.

In conclusion, historically rabies-free urban areas among dogs and cats may be exposed to new disease cycles, sylvatic-aerial, as a result of recent changes in nonhematophagous bat behavior. Reemerging cases of rabies in disease-free urban areas warns of the importance of mass vaccination of dogs and cats, in association with continuous monitoring of nonhematophagous bats found during the daytime or in unexpected locations. Finally, negative DIF results for rabies must always be followed by at least 21-day biological testing in mice.

ACKNOWLEDGMENTS

The authors kindly thank the Pasteur Institute of the State of São Paulo for their diagnostic support regarding rabies virus characterization and the Epidemiology Center of the Municipal Health Secretariat of Curitiba for providing epidemiological data.

CONFLICT OF INTEREST

The authors declare that there is no conflict of interest.

REFERENCES

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Lei nº. 9605. Dispõe sobre as sanções penais e administrativas derivadas de condutas e atividades lesivas ao meio ambiente, e dá outras providências (Feb 12, 1998). [cited 2010 Aug 20]. Available from: http://www.planalto.gov.br/ccivil_03/Leis/L9605.htm.

Address to:

Dra. Vivien Midori Morikawa

Lab. Doenças Parasitárias/Deptº. Medicina Veterinária/UFPR

Rua dos Funcionários 1540, Cabral

80035-050 Curitiba, PR, Brasil

Phone: [phone]

e-mail: [email protected]

Received in 21/11/2010

Accepted in 10/01/2011