An area 30 by 50 km was selected for destruction of vampire bats (Desmodus rotundus). The area was located in the path of an advancing epizootic of vampire bat-borne bovine rabies which had been moving southward at the average rate of 40 km per year for 14 years. The bats were exterminated in their roosts in water wells with cyanide gas, and the wells were sealed with wire mesh frames. The epizootic did not pass through the control area, but did pass it by to the west. It is concluded that strategic elimination of vampire bats may be used for control of bovine rabies when vampires are the sole vector.
In this study, 91 strains isolated in the River Plate Basin, South America, were examined from the epidemiological standpoint and with monoclonal antibodes (MAbs) to the nucleocapsid of rabies virus. Such strains reacted to MAbs in accordance with nine different patterns (antigenic variants). Rabies virus was isolated from 49 cattle, 21 dogs, 11 non-haematophagous bats, four vampire bats, two foxes, two horses, one buffalo, and one human. Five of the variants had not been described previously. It was also found that two cases of rabies in wild foxes (Ctrdoyon thous) which had attacked persons in the Province of Chaco, Argentina, had been caused by variants from dog and vampire bat, while two cases in frugivorous bats (4rtibeus lituratus) from Argentina and Brazil, had been infected by vampire bat variants. In addition, symptoms shown by cattlc infected with strains which reacted as originating in canine vectors, differed from those observed in bovines from which the variants isolated corresponded to vampire bats.
The inactivation dynamics of rabies virus (PV strain) by binary ethylenimine, and the immunogenic properites and the stability of the vaccines prepared using this agent, were studied. Binary ethylenimine at a final concentration of 0.01 M was prepared wtih 2-bromoethylamine hydrobromide in alkaline solutions, either separately from or in suspensions of rabies virus propagated in BHK cells. The infectivity of virus suspensions containing more than 108 plaque-forming units per 0.1 ml was inactivated in 2 h when the inactivating agent was prepared before its addition to the suspensions, and in3 h when prepared directly in the suspensions. Liquid vaccines prepared in this manner and stored at different temperatures maintained potency for 1 month at 37 degrees C and for 6 months at 4 degrees C and 22 to 25 degrees C. Lyophilized vaccine maintained its potency for 6 months at the three temperatures. The inactivated vaccine mixed with aluminum or oil adjuvant at high dilutions protected guinea pigs against challenge. This safer procedure for rabies virus inactivation offers promise for the production of effective vaccines for the immunization of dogs and cattle.
A tissue culture system for detecting rabies virus from saliva samples of suspected animals was developed and compared to suckling mouse inoculation. Swab samples were obtained from the mouth of the animal heads received for rabies diagnosis; these swabs were submerged in maintenance medium. The maintenance medium was inoculated intracerebrally into suckling mice and onto BHK-21 cells with diethylaminoethyl (DEAE)-dextran (BHK/DEAE) and without (BHK). Rabies immunofluorescence was performed on the brain of the mice dying during the observation period and also on both tissue culture systems every day after infection. The BHK-DEAE system detected 28 positive samples obtained from 48 rabid animals and the BHK system detected 18. By suckling mouse inoculation only 11 of the same positive samples were detected. A total of 90 samples was studied by the three methods. Rabies virus was detected by the tissue culture methods earlier than by suckling mouse inoculation. The BHK-DEAE method was an economic and fast method for rabies virus detection in saliva samples, which could be used for ecological and pathogenesis studies, as well for rabies diagnosis before the death of the suspected animal.
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