A Tick Vector Transmission Model of Monocytotropic Ehrlichiosis.

BACKGROUND: Ehrlichioses are emerging, tick-borne diseases distributed worldwide. Previously established animal models use needle inoculation as a mode of infection; however, there is limited representation of natural transmission in artificially inoculated models compared with transmission by the tick vector. The objective of this study was to develop a tick vector transmission animal model of ehrlichial infection using a human pathogen, Ehrlichia muris-like agent (EMLA). METHODS: Ixodes scapularis larvae were fed on EMLA-infected mice, and after molting, infected nymphs were used to infest naive animals. RESULTS: Ehrlichiae were acquired by 90%-100% of feeding larvae. The majority of animals fed upon by infected nymphs developed sublethal infection with 27% lethality. Bacteria disseminated to all tissues tested with greatest bacterial loads in lungs, but also spleen, lymph nodes, liver, kidneys, brain, and bone marrow. Numerous foci of cellular infiltration, mitoses, and hepatocellular death were observed in liver. Mice infected by tick transmission developed higher antiehrlichial antibody levels than needle-inoculated animals. Tick-feeding-site reactions were observed, but there was no observed difference between animals infested with infected or uninfected ticks. CONCLUSIONS: For the first time we were able to develop a tick transmission model with an Ehrlichia that is pathogenic for humans.

An animal model of a newly emerging human ehrlichiosis.

BACKGROUND: Human ehrlichioses are emerging life-threatening diseases transmitted by ticks. Animal models have been developed to study disease development; however, there is no valid small animal model that uses a human ehrlichial pathogen. The objective of this study was to develop a mouse model for ehrlichiosis with the newly discovered human pathogen, Ehrlichia muris-like agent (EMLA). METHODS: Three strains of mice were inoculated with different doses of EMLA by the intravenous, intraperitoneal, or intradermal route and evaluated for clinical and pathologic changes during the course of infection. RESULTS: EMLA infected C57Bl/6, BALB/c, and C3H/HeN mice and induced lethal or persistent infection in a route- and dose-dependent manner. The clinical chemistry and hematologic changes were similar to those of human infection by Ehrlichia chaffeensis or EMLA. Bacterial distribution in tissues differed after intradermal infection, compared with the distribution after intravenous or intraperitoneal injection. Lethal infection did not cause remarkable pathologic changes, but it caused fluid imbalance. EMLA infection of endothelium and mononuclear cells likely plays a role in the severe outcome. CONCLUSIONS: The EMLA mouse model mimics human infection and can be used to study pathogenesis and immunity and for development of a vector transmission model of ehrlichiosis.

Diagnóstico sorológico de erliquiose canina com antígeno brasileiro de Ehrlichia canis / Serological diagnosis of canine monocytic ehrlichiosis with Brazilian antigen of Ehrlichia canis

O presente trabalho relata o isolamento de Ehrlichia canis em cultivo de células DH82 e posterior padronização da Reação de Imunofluorescência Indireta (RIFI). Leucócitos de uma cadela experimentalmente infectada com o isolado Jaboticabal de E. canis foram inoculados em cultivo de células DH82. A inoculação foi monitorada após a segunda semana, a cada 5-6 dias, através de exames citológicos e pela amplificação de um fragmento do gene dsb de Ehrlichia pela Reação em Cadeia pela Polimerase (PCR) para confirmação da infecção. A cultura apresentou-se positiva aos 27 dias pós-inoculação pela PCR e aos 28 dias pela citologia. No 33o dia pós-inoculação, observou-se 20 por cento de células infectadas e, aos 53 dias, 60 por cento de infecção. Atualmente, o isolado encontra-se estabelecido em células DH82, com várias passagens atingindo 90-100 por cento de células infectadas entre 7-10 dias após a inoculação. Após o seqüenciamento do produto de PCR, o isolado apresentou-se 100 por cento similar à seqüência correspondente de E. canis depositada no GenBank. As células infectadas foram utilizadas como antígeno para a padronização da RIFI para detecção da infecção em cães.

The present study describes a successful isolation of Ehrlichia canis and its establishment in DH82 cells, followed by the development of an Indirect Fluorescent Antibodies Test (IFAT). Leukocytes collected from an experimentally infected dog with the Jaboticabal strain of E. canis were used to inoculate a DH82 cell monolayer. Two weeks later, the inoculated culture was checked for infectivity, every 5-6 days by both cytological staining and PCR, targeting a fragment of the dsb gene. The cell culture showed to be infected by Ehrlichia on day 27 by PCR and on day 28 by cytological staining. By the day 33, the infection rate reached 20 percent and on day 53, 60 percent. Currently, the isolate is established in DH82 cells, with several passages reaching 90-100 percent of infected cells, within 7 to 10 days post inoculation. After sequencing, the amplicon was identical to other E. canis corresponding sequences available in the GenBank. DH82 infected cells were used to standardize an IFAT for the diagnosis of canine ehrlichiosis.

Simultaneous canine distemper encephalitis and canine parvovirus infection with distemper-associated cardiac necrosis in a pup

Simultaneous infection of canine distemper virus and canine parvovirus associated with distemper myocardial degeneration and necrosis is described in a pup. The dog demonstrated myoclonus, nystagmus, enamel hypoplasia, abdominal pustules, and bilateral corneal ulceration clinically. Demyelinating encephalitis, myocardial degeneration and necrosis with mineralization, and necrosis, hemorrhage and fusion of intestinal villi were observed. The lesions observed in this dog are characteristic of a dual infection of canine distemper virus and canine parvovirus