Vaccination of dogs with canine parvovirus type 2b (CPV-2b) induces neutralising antibody responses to CPV-2a and CPV-2c.

Since the identification of canine parvovirus type 2, three variants have subsequently been observed differing from the historical CPV-2 and each other by 1-2 amino acids only. As a result there has been considerable research into differential diagnostics, with some researchers indicating there is a need for new vaccines containing different strains of CPV-2. In this study we investigated whether vaccination with a CPV-2b containing vaccine would induce cross-reactive antibody responses to the other CPV-2 variants. Two studies where dogs were vaccinated with a multivalent vaccine, subsequently challenged with CPV-2b and sera samples analysed are presented. Six week old pups with defined serological status were vaccinated twice, three weeks apart and challenged either 5 weeks (MDA override study) or one year after vaccination (duration of immunity study). Sera samples were collected before each vaccination and at periods throughout each study. In each study the antibody profiles were very similar; serological responses against CPV-2a, CPV-2b and CPV-2c were higher than those for CPV-2. Nevertheless, responses against CPV-2 were well above levels considered clinically protective. In each study dogs also showed a rapid increase in antibody titres following vaccination, reached a plateau following second vaccination with a slight decline to challenge after which rapid anamnestic responses were seen. Evaluation of the serological responses suggests vaccination with CPV-2b would cross-protect against CPV-2a and CPV-2c, as well as against CPV-2 which is now extinct in the field. In conclusion we have demonstrated that vaccination of minimum aged dogs with a multivalent vaccine containing the CPV-2b variant strain will induce serological responses which are cross-reactive against all currently circulating field strains, CPV-2a and CPV-2c, and the now extinct field strain CPV-2.

Duration of immunity of a multivalent (DHPPi/L4R) canine vaccine against four Leptospira serovars.

Despite effective vaccines against common Leptospira serovars, the development of new products with long duration of immunity is still important to protect dogs against leptospirosis. The results from four challenge studies performed one year after vaccination of dogs with a multivalent vaccine containing four Leptospira antigens are reported. Six week old dogs received two vaccinations, three weeks apart, and were challenged 367 days later. Clinical observations were recorded, while blood (culture, biochemistry and haematology), urine (culture) and liver and kidney (culture) samples were collected throughout the study or at necropsy. All control dogs remained seronegative until challenge, when they seroconverted. Antibody titres to Leptospira antigens were seen in vaccinated dogs 21 days after first vaccination and peaked three to six weeks after the second vaccination. Titres decreased in all studies over the following 12 months, until challenge when anamnestic responses were observed. In all studies control dogs demonstrated various abnormal clinical signs, while no vaccinated dogs were affected; differences between groups were only significant following L. bratislava challenge. Analysis of blood cultures showed all control and five of the 24 vaccinated dogs were Leptospira positive after challenge; all studies showed significant differences between treatment groups in mean number of days with positive cultures. Significant differences between vaccinated and control groups in mean number of days with positive urine cultures were also observed, with all non-vaccinated and one vaccinated dog Leptospira positive. The urine culture positive vaccinated dog also gave positive culture from kidney and liver samples. All except one control dog also showed positive Leptospira isolation from kidney or liver, with significant differences between vaccinated and control groups observed. The results demonstrate that administration of a new vaccine to six week old puppies induces immunity which is still effective up to one year later as demonstrated by challenge.

A new multivalent (DHPPi/L4R) canine combination vaccine prevents infection, shedding and clinical signs following experimental challenge with four Leptospira serovars.

Although effective vaccines have been developed against the common Leptospira serovars, they are still reported in clinical cases, while others are increasingly prevalent. The results from four challenge studies following vaccination of dogs with a new combination vaccine (DHPPi/L4R) containing inactivated L. serovars, L. canicola, L. icterohaemorrhagiae, L. bratislava and L. grippotyphosa conducted to satisfy the requirements of the European Pharmacopoeia monograph (01/2008:0447), are reported. Six week old dogs received two vaccinations, three weeks apart, and were challenged 25 days later with different isolates of the L. serovars. Clinical observations were recorded, and blood, urine and tissue samples were collected for analysis. Following challenge, non-vaccinated dogs demonstrated various clinical signs, while no vaccinated dogs were affected; significant differences in mean clinical scores were observed. Measurable antibody titres to each Leptospira antigen were seen in vaccinated dogs 21 days following the first vaccination, with further increases in antibody titres observed following challenge with the respective Leptospira strain. Non-vaccinated dogs remained seronegative until challenge. Leptospira were re-isolated from the blood, urine, kidney and liver of all non-vaccinated dogs following challenge. In contrast no vaccinated dogs had Leptospira re-isolated from the same tissues. Significant differences were seen in number of days with positive isolation (blood and urine) and in number of dogs with positive samples (kidney and liver). In conclusion, vaccination of dogs with the new vaccine induces protective immunity 25 days after second vaccination with protection against infection, renal infection and clinical signs following challenge.