Partial VP2 sequencing of canine parvovirus (CPV) strains circulating in the state of Rio de Janeiro, Brazil: detection of the new variant CPV-2c

Canine parvovirus (CPV) is the most important enteric virus for dogs and it seems to be undergoing continuous evolution, generating new genetic and antigenic variants throughout the world. The aim of this study was to analyze the distribution of CPV variants from 1995 to 2009 and to investigate the circulation of the new variant CPV-2c in Rio de Janeiro, Brazil. In addition, the clinical features of CPV infection were also reported. After CPV laboratorial confirmation by HA/HI and PCR, thirty-two fecal samples were analyzed by sequencing a 583-bp fragment of the VP2 gene. One sample, collected in 2008 was typed as the new type CPV-2c. All samples from 1995 to 2003 were identified as "new CPV-2a". From 2004 to 2006, both "new CPV-2a" and CPV-2b were observed. From 2006 to 2009, most of the samples were characterized as CPV-2b. The classical signs of CPV enteritis were observed in 16/18 CPV-2a and 5/13 CPV-2b infected puppies. These results show that continuous epidemiological surveillance of CPV strain distribution is essential for studying the patterns of CPV-2a and 2b spread and for determining whether the new variant CPV-2c has become permanently established in Brazilian canine population.

Genomic typing of canine parvovirus circulating in the State of Rio de Janeiro, Brazil from 1995 to 2001 using polymerase chain reaction assay

In this study, the genomic types of canine parvovirus (CPV) circulating in the State of Rio de Janeiro, Brazil, from 1995 to 2001, were investigated using the polymerase chain reaction assay (PCR). A total of 78 faecal samples from gastroenteritic puppies, confirmed as positive for canine parvovirus by haemagglutination/haemagglutination inhibition tests or virus isolation in cell culture (MDCK), were examined. The viral DNA was extracted from faecal samples using a combination of phenol- chloroform and silica-guanidine thiocyanate methods. PCR was carried out with differential pairs of primers to distinguish the old (CPV-2) and new types of virus (CPv-2a or CPV-2b). Specific amplicons were observed for all samples using the primer pair P2ab, which detects CPV-2a and CPV-2b. Seventy-six from a total of 78 samples (97%) were considered as CPV-2b because of their reaction with the primer pair P2b. Thirty samples (30/78) were from previously vaccinated puppies and in 15 of them the enteritis symptoms began from 1 to 12 days after vaccination. PCR confirmed the infection by wild virus (CPV-2b) in 5 of these 15 puppies who had received old-type vaccines. Our results show that CPV-2b was the prevalent type circulating in the State of Rio de Janeiro from 1995 to 2001.

Kidney ultrastructural lesions in dogs experimentally infected with Dirofilaria immitis (Leidy, 1856)

Kidneys of 16 beagles with experimentally induced heartworm (Dirofilaria immitis) infections and 4 heartworm-nai;ve dogs were studied by light and electron microscopy. The infections were induced either by subcutaneous injection of infective larvae or by the transplantation of adult parasites, and infection periods varied from 111 to 818 days and 365 to 923 days, respectively. One control group of heartworm-naïve dogs and four groups of heartworm-infected dogs, which were divided according to the type and the length of infection, were used. In the infected dogs, thickening of the glomerular basement membrane (GBM), the presence of dense deposits in the GBM, and foot process effacement were the most frequent lesions observed. In some dogs, electron dense deposits were seen in the GBM and the mesangium and/or enlargement of the mesangial matrix could be characterized. The longer the infection period, the thicker the GBM and the more common the occurrence of foot process effacement. In general, these alterations were more evident in animals that had been infected for more than 1 year, had high microfilaremia, and had 14 or more parasites in the main pulmonary artery and its branches. The presence of dense deposits suggests that the pathogenesis of kidney disease in dirofilariasis is associated with deposits of immune complexes in the membrane. The finding of ultrastructural changes in dogs with early prepatent infections suggests that immature heartworms, as well as microfilariae and possibly adult worms, contribute to the glomerulonephropathy.

Biological control of tick populations: review and reflections

This study is concerned with aspects of the relationship between ticks and their hosts that have a bearing on biological control of tick populations. It proposes control methods based on a program that would combine development of an effective vaccine with genetic selection of hosts.

Cross-reaction of tick salivary antigens in the Boophilus microplus-cattle system

Calves were immunized with Boophilus microplus saliva, filtered through Millipore membranes, in Freund's complete adjuvant. Serum samples were tested by passive hemagglutination against Babesia bigemina, Anaplasma marginale, B. microplus larvae extract, Stomoxys calcitrans extract and B. microplus saliva. After immunization, titers to saliva, larval tick-extract and to S. calcitrans were increased. The challenge with live tick larvae enhanced the formation of antibodies against larva extract, fly extract and tick saliva, which supports the idea that under natural controlled conditions this cross-reactivity could occur.