Avelino Albas

Vírus da raiva em quirópteros naturalmente infectados no Estado de São Paulo, Brasil

OBJECTIVE To identify the species of bats involved in maintaining the rabies cycle; to investigate the distribution of the rabies virus in the tissues and organs of bats and the time taken for mortality among inoculated mice. METHODS From April 2002 to November 2003, bats from municipalities in the State of São Paulo were screened for the presence of the rabies virus, by means of direct immunofluorescence. The virus distribution in the bats was evaluated by inoculating mice and N2A cells with 20% suspensions prepared from fragments of different organs and tissues, plus the brain and salivary glands. The time taken for mortality among the mice was monitored daily, following intracerebral inoculation. RESULTS Out of the 4,395 bats received, 1.9% were found positive for the rabies virus. They belonged to ten genera, with predominance of insectivores. The maximum mean times taken for mortality among the mice following inoculation with brain and salivary gland material were 15.33+/-2.08 days and 11.33+/-2.30 days for vampire bats, 16.45+/-4.48 days and 18.91+/-6.12 days for insectivorous bats, and 12.60+/-2.13 days and 15.67+/-4.82 days for frugivorous bats, respectively. CONCLUSIONS The species infected with the rabies virus were: Artibeus lituratus, Artibeus sp., Myotis nigricans, Myotis sp., Eptesicus sp., Lasiurus ega, Lasiurus cinereus, Nyctinomops laticaudatus, Tadarida brasiliensis, Histiotus velatus, Molossus rufus, Eumops sp. and Desmodus rotundus. Virus investigation in the different tissues and organs showed that the brain and salivary glands were the most suitable sites for virus isolation.

Molecular and geographic analyses of vampire bat-transmitted cattle rabies in central Brazil

BackgroundVampire bats are important rabies virus vectors, causing critical problems in both the livestock industry and public health sector in Latin America. In order to assess the epidemiological characteristics of vampire bat-transmitted rabies, the authors conducted phylogenetic and geographical analyses using sequence data of a large number of cattle rabies isolates collected from a wide geographical area in Brazil.MethodsPartial nucleoprotein genes of rabies viruses isolated from 666 cattle and 18 vampire bats between 1987 and 2006 were sequenced and used for phylogenetic analysis. The genetic variants were plotted on topographical maps of Brazil.ResultsIn this study, 593 samples consisting of 24 genetic variants were analyzed. Regional localization of variants was observed, with the distribution of several variants found to be delimited by mountain ranges which served as geographic boundaries. The geographical distributions of vampire-bat and cattle isolates that were classified as the identical phylogenetic group were found to overlap with high certainty. Most of the samples analyzed in this study were isolated from adjacent areas linked by rivers.ConclusionThis study revealed the existence of several dozen regional variants associated with vampire bats in Brazil, with the distribution patterns of these variants found to be affected by mountain ranges and rivers. These results suggest that epidemiological characteristics of vampire bat-related rabies appear to be associated with the topographical and geographical characteristics of areas where cattle are maintained, and the factors affecting vampire bat ecology.

Bat rabies in the north-northwestern regions of the state of São Paulo, Brazil: 1997-2002

OBJECTIVE Reports on bat rabies in Brazil are sporadic and isolated. This study aimed at describing the detection of rabies virus in bats in the state of São Paulo. METHODS A total of 7,393 bats from 235 municipalities of the north and northwestern areas of the state of São Paulo, Southeastern Brazil, were assessed according to their morphological and morphometric characteristics from 1997 to 2002. Fluorescent antibody test and mice inoculation were used for viral identification. RESULTS Of all samples examined, 1.3% was rabies virus positive, ranging from 0.2% in 1997 to 1.6% in 2001. There were found 98 bats infected, 87 in the urban area. Fluorescent antibody test was detected in 77 positive samples, whereas 92 produced rabies signs in mice; incubation period ranging from 4 to 23 days. In 43 cities at least one rabid bat was observed. The highest proportion (33.7%) of rabies virus was found in Artibeus lituratus. Eptesicus and Myotis were the most frequent positive species (24.5%) of the Vespertilionidae family. The species Molossus molossus and Molossus rufus showed 14.3% positive bats. There were no differences in the distribution of positive rabies between females (33; 48.5%) and males (35; 51.5%). CONCLUSIONS Rabies-infected bats were found in environments that pose a risk to both human and domestic animal population and there is a need for actions aiming at the control of these species and public education.

Antigen profile of rabies virus isolated from different species of non-hematophagous bats in the region of Presidente Prudente, State of São Paulo

Using the monoclonal antibody technique, the Clinical and Molecular Virology Laboratory of the Institute of Biomedical Sciences of the University of São Paulo typed 18 rabies virus samples from non-hematophagous bats of several species from the region of Presidente Prudente, SP, Brazil. Among these samples, 15 (82.3%) were defined as variant 3 (compatible with samples isolated from Desmodus rotundus bats) and three (16.7%) as variant 4 (compatible with samples isolated from Tadarida brasiliensis bats).

Diagnóstico laboratorial da raiva na região oeste do Estado de São Paulo

The Pólo da Alta Sorocabana laboratory, Presidente Prudente, SP, Brazil, and the Biological Institute in São Paulo State, performed an evaluation of rabies diagnosis from 1996 to 2003 in the west region of São Paulo State. For the tests, the laboratories used direct immunofluorescence and mice inoculation in 4,950 samples, that were sent for analysis involving dogs, cats, cattle, chiroptera (bats) and other animals. According to the results, the laboratories found 74 positive samples; of which 58 (78.4%) were non-hematophagous bats and 16 (21.6%) related to cattle. The present epidemiological study verified that in spite of the high positive index in chiroptera compared to the other species, there was not an outbreak of rabies in the species in the region of Presidente Prudente, from 1996 to 2003 but a rise in the positive index due to a marked increase in the number of chiroptera samples sent to the laboratories for virus rabies research.

Effect of a booster-dose of rabies vaccine on the duration of virus neutralizing antibody titers in bovines

Humoral immune response using inactivated rabies vaccine was studied in 35 nelore cross-bred bovines of western region of São Paulo state. Ninety days after vaccination, 13 (92.8%) animals presented titers > or = 0.5 IU/ml, through mouse neutralization test. After 180 days, 9 (64.3%) sera showed titers > or = 0.5 IU/ml, after 270 days, only one (7.1%) showed a titer of 0.51 IU/ml, and after 360 days, all animals showed titers < 0.5 IU/ml. Group of animals receiving booster dose 30 days after vaccination presented, two months after, all with titers > 0.5 IU/ml. At 180 days, 17 (80.9%) sera presented titers > 0.5 IU/ml; at 270 days, 15 (71.4%), with titers > or = 0.5 IU/ml and at 360 days, 4 (19.0%), with titers > or = 0.5 IU/ml. Booster-dose ensured high levels of neutralizing antibodies for at least three months, and 240 days after revaccination, 71.4% of animals were found with titers > or = 0.5 IU/ml.

Efficiency of Matricaria chamomilla CH12 and number of doses of rabies vaccine on the humoral immune response in cattle.

This study evaluated the effect of Matricaria chamomilla and vaccination frequency on cattle immunization against rabies. Four groups (n = 15 /group) were treated with or without Matricaria chamomilla CH12 and vaccinated with one or two doses of rabies vaccine (30 day interval). No effect of chamomile was found on cattle immunization against rabies; however, antibody titers were protective in cattle vaccinated twice, while 93.3% of cattle vaccinated only once had titers under 0.5 UI/ml after 60 days. In conclusion, the use of chamomile did not alter the humoral immune response in cattle, and two vaccine doses are suggested for achieving protective antibody titers.

Os morcegos e a raiva na região oeste do Estado de São Paulo

INTRODUCTION: The Polo da Alta Sorocabana Laboratory in Presidente Prudente, SP, in partnership with other research institutions, conducted studies related to bats from the western region of the State of Sao Paulo, Brazil. Thus, certain situations were investigated, including: a) isolation of the rabies virus from 2006 to 2008; b) identification of respective antigenic variants; and c) characterization of daytime shelters of Desmodus rotundus vampire bats. METHODS: Samples for examination originated from nonhematophagous bats forwarded to the laboratory and subjected to direct fluorescent antibody test and mouse inoculation test. Positive samples were characterized by the monoclonal antibody test. Regarding the bats, they were identified and classified and mapping of their shelters was also performed. RESULTS: The laboratory received 1,113 nonhematophagous bats for rabies diagnosis, 11 (1%) of which were positives, and among the positive samples, 5 (45.5%) presented antigenic variant 3 (from the bat Desmodus rotundus) and 4 (36.5%) were compatible with samples derived from Brazilian insectivorous bats. Sixteen vampire bat shelters were investigated and observation confirmed the presence of another 3 species of nonhematophagous bats coexisting with them. CONCLUSIONS: The experiments showed that at least 3 antigenic variants of rabies virus are circulating in the region and that the cohabitation of vampire bats with nonhematophagous bats could be related to the dissemination of the rabies virus.

Interval between first dose and booster affected antibody production in cattle vaccinated against rabies

In this study, we compared the levels of neutralizing antibodies induced by inactivated rabies vaccine in cattle by using three alternative immunization procedures. Forty-five bovines (breed nelore) were then organized in three groups (A, B and C, with 15 animals/group). Group A received only one vaccine dose at day zero and Group B received the first dose at day zero and then another dose at day 30 (early booster). Group C was also immunized with two doses; however, the booster was postponed until day 180 after the first dose (delayed booster). Blood samples were withdrawn at days zero (before the first dose) and 30, 210, 390, and 540 after the beginning of immunization and the antibody titers were evaluated by mouse neutralization test. The protocol used to immunize Group C (booster at day 180) was clearly more efficient. In this group, antibody levels were higher and also remained higher for longer periods in comparison with the other two groups. These results show that booster timing significantly affected antibody levels. Therefore, programs addressed to control this disease in cattle should consider not only the use of a booster but also its administration time.

Imunofluorescência realizada em cérebros de camundongos infectados com vírus rábico - cepa CVS, em diferentes estágios de decomposição

O teste de imunofluorescencia (IF) foi avaliado na deteccao de virus rabico presente em cerebros de carcacas de camundongos infectados com virus da cepa CVS, os quais foram conseguidos atraves de uma combinacao de tratamentos, em que se variaram as temperaturas (4,25 e -20oC) e o tempo de armazenamento. No teste de IF realizado com impressoes cerebrais de carcacas que haviam sido submetidas a temperatura de 25oC por 12 -18 h, houve maior dificuldade de visualizacao imediata dos corpusculos de inclusao, enquanto que nos materiais conservados a 4oC por ate 48 h, as inclusoes foram facilmente reconhecidas. Carcacas mantidas a -20oC mantiveram-se viaveis a identificacao pela IF mesmo apos terem sido armazenadas por 720 h quando foram feitas as ultimas observacoes. Em carcacas mantidas a 25oC por 10 h, com tratamento posterior a 4 e -20oC, o antigeno rabico nao pode ser identificado atraves da IF, em consequencia da decomposicao das carcacas que ocorrem, respectivamente, apos 10 e 24 h. Recomenda-se, portanto, empregar o teste de IF, em carater de rotina, no controle de qualidade da vacina contra a Raiva, no que diz respeito a prova de virus residual (teste de verificacao da inativacao viral), de vez que ele permite esclarecer mortes assintomaticas ocorridas em animais inoculados com a vacina, durante o periodo de observacao da prova (21 dias), bem como evitar a sua repeticao quando essas mortes ocorrem, o que representa consideravel economia de tempo.