Comparative Evaluation of the Vector Competence of Four South American Populations of the Rhipicephalus sanguineus Group for the Bacterium Ehrlichia canis, the Agent of Canine Monocytic Ehrlichiosis

This study compared the vector competence of four populations of Rhipicephalus sanguineus group ticks for the bacterium Ehrlichia canis, the agent of canine monocytic ehrlichiosis (CME). Ticks (larvae and nymphs) from the four populations-one from São Paulo state, southeastern Brazil (BSP), one from...

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Bibliographic Details
Published in:PloS one 2015-09, Vol.10 (9), p.e0139386-e0139386
Main Authors: Moraes-Filho, Jonas, Krawczak, Felipe S, Costa, Francisco B, Soares, João Fábio, Labruna, Marcelo B
Format: Article
Language:English
Subjects:
Adults
Anaplasma
Animals
Arachnids
Causes of
Comparative analysis
Deoxyribonucleic acid
Development and progression
Disease prevention
Disease transmission
Disease Vectors
Diseases and pests
DNA
Dog Diseases - microbiology
Dogs
Ehrlichia
Ehrlichia canis
Ehrlichia canis - physiology
Ehrlichiosis
Ehrlichiosis - microbiology
Ehrlichiosis - veterinary
Epidemiology
Feeding
Health aspects
Infections
Infestation
Larva - microbiology
Larvae
Molting
Monocytes
Nymphs
Physiological aspects
Polymerase chain reaction
Populations
Real-Time Polymerase Chain Reaction
Rhipicephalus sanguineus
Rhipicephalus sanguineus - microbiology
Studies
Ticks
Vectors
Vectors (Biology)
Veterinary medicine
Zoonoses
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Summary:This study compared the vector competence of four populations of Rhipicephalus sanguineus group ticks for the bacterium Ehrlichia canis, the agent of canine monocytic ehrlichiosis (CME). Ticks (larvae and nymphs) from the four populations-one from São Paulo state, southeastern Brazil (BSP), one from Rio Grande do Sul state, southern Brazil (BRS), one from Argentina (ARG), and one from Uruguay (URU)-were exposed to E. canis infection by feeding on dogs that were experimentally infected with E. canis. Engorged ticks (larvae and nymphs) were allowed to molt to nymphs and adults, respectively, which were tested by molecular analysis (E. canis-specific PCR assay) and used to infest naïve dogs. Through infestation of adult ticks on naïve dogs, after nymphal acquisition feeding on E. canis-infected dogs, only the BSP population was shown to be competent vectors of E. canis, i.e., only the dogs infested with BSP adult ticks developed clinical illness, seroconverted to E. canis, and yielded E. canis DNA by PCR. This result, demonstrated by two independent replications, is congruent with epidemiological data, since BSP ticks were derived from São Paulo state, Brazil, where CME is highly endemic. On the other hand, BRS, ARG, and URU ticks were derived from a geographical region (South America southern cone) where CME has never been properly documented. Molecular analysis of unfed adults at 30 days post molting support these transmission results, since none of the BRS, ARG, and URU ticks were PCR positive, whereas 1% of the BSP nymphs and 31.8% of the BSP adults contained E. canis DNA. We conclude that the absence or scarcity of cases of CME due to E. canis in the South America southern cone is a result of vector incompetence of the R. sanguineus group ticks that prevail on dogs in this part of South America.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0139386