Secretion Of Rabies Virus In Saliva And Its Tissue Distribution In Challenged Dogs

Rabies virus (RABV) is a highly neurotropic pathogen and can cause fatal infection in almost all warm blood animals, primarily through the bite of a rabid animal. After multiplication in the CNS, RABV can spread to the salivary glands where it continues its multiplication and is secreted into saliva. Rabid dogs are the main transmission source; however, the secretion in saliva and tissue distribution of RABV in rabid dogs have not been well investigated. In the present study two groups of beagle dogs with five in each were injected in the left and right masseter muscles with one of two strains of street rabies virus:SDJN02(from a rabid cow) and SXTYD01(from a rabid dog). The dogs were observed for clinical symptoms twice daily at about6hrs’interval, and saliva swabs were collected at each observation. Following death from rabies, their brain, spinal cord, salivary glands (mandibular,parotid and zygomatic glands), tongue, masseter muscles of the injection sites, heart, liver, spleen, lung, kidney and intestinal contents were collected. Taqman real time RT-PCR, RT-PCR, IFA and RTCIT were used to detect RABV in collected specimens. While one animal (SXTYD01) survived without developing the disease, and producing a high neutralizing antibody response, the remaining9suffered rabies post challenge with none producing neutralizing antibody. The two rabies strains exhibited differences in incubation time and clinical signs. SDJN02caused disease5to11days post challenge with moaning, body and head trembling and intensified salivation, whereas SXTYD01caused disease12to18days post challenge with depression and increased aggression as the most common symptoms. RABV was present in brain tissues, spinal cord, tongue and masseter muscles of all8rabid dogs and in the salivary glands of6/8(75%). Surprisingly,3/8(38%) rabid dogs showed RABV positive in the internal organs with1/8intestinal content positive, and2of them also secreted, intermittently, the virus into saliva (22%).The remaining7/9did not shed virus into the saliva at any time point of the experiment. Rabies virus infection of the internal organs as well as shedding in saliva were observed only for strain SXTYD01, not SDJN02. In conclusion, while highly neurotropic, RABV can also be present in internal organs and non-neural tissues following infection. Additionally, our observations indicate that RABV may not be secreted into the saliva of rabid dogs as commonly as previously believed.