Serological responses of adult dogs to revaccination against distemper, parvovirus and rabies

Prevalence of Serum Antibody Titers against Core Vaccine Antigens in Italian Dogs

Canine vaccination is the main tool for preventing dangerous and widespread diseases. The strongly recommended (core) dog vaccines are against Canine Parvovirus type 2 (CPV-2), Canine Distemper Virus (CDV), and Canine Adenovirus (CAdV-1), but vaccination protocols should be tailored to dog lifestyles. Vaccination guidelines suggest vaccinating adult dogs no more frequently than every 3 years using modified live (attenuated) vaccines (MLV), thus obtaining a long-lasting (sometimes throughout life) specific protection in many but not all animals. The aim of this study was to determine the actual levels of seroprotection against CPV-2, CDV and CAdV-1 in a cohort of Italian dogs by using the in-practice test VacciCheck. A total of 1,027 dogs (951 vaccinated and 76 unvaccinated) were analyzed for Protective Antibody Titers (PATs) against CPV-2, CDV, and CAdV-1. Differences related to sex, age, breed size, health status, and time elapsed since last vaccination were evaluated. Half of the entire canine cohort (50.6%) had PATs for all three viruses (68.5% considering only vaccinated dogs). In particular, 90.8% of dogs were protected against CPV-2, 68.6% against CDV, and 79.8% against CAdV-1. Most dogs remained protected for 3 years after vaccination or longer. Revaccination on a 3-year basis can then be recommended for core MLV vaccines without altering individual's seroprotection or even herd immunity.

[Optimization of rabies (Rhabdoviridae: Lyssavirus) dog vaccination schedule using a mathematical model]

INTRODUCTION

Most cases of human rabies are caused by dog (Canis lupus familiaris) bites. Therefore, the implementation of vaccination programs of these animals is one of the urgent tasks.The work aims to identify the factors influencing the production of antirabies virus-neutralizing antibodies (VNAs) in vaccinated dogs, and to formulate recommendations for adjusting the vaccination schedule using mathematical modeling (MM).

MATERIAL AND METHODS

We used a fixed-effects modeling procedure to estimate the two-compartment model parameters using log-transformed data (obtained by RFFIT, rapid fluorescent focus inhibition test; and FAVN, fluorescent antibody virus-neutralization test) on the VNAs levels in the serum of vaccinated dogs.

RESULTS

More vigorous immune response after a two-dose primary vaccination is formed in juvenile dogs at the age of 3 months to 1 year compared to the adult dogs. Following the primary vaccination and revaccination 1 year after, VNAs were produced more intensively in adult stray dogs than in domestic dogs.

DISCUSSION

The short-term immune response observed in dogs aged up to 3 months is due to the presence of colostral antibodies and the active growth of the organism at this age. The results of our study confirm that most of the dogs have a level of antirabies VNAs of ≥0.5 IU/ml up to two or more years following immunization. However, only regular annual revaccination ensures the protective VNAs level in animals that responded poorly to vaccination due to various factors.

CONCLUSION

The following antirabies vaccination schedule is recommended: primary vaccination of the dog at the age of 3 months up to 1 year with 1-2 month intervals, then revaccination annually. This work also demonstrates the possibility of a wider application of MM methods for solving problems of vaccine prevention.

Prevalence of Neutralizing Antibodies to Canine Distemper Virus and Response to Vaccination in Client-Owned Adult Healthy Dogs

Re-vaccinations against canine distemper virus (CDV) are commonly performed in 3-year intervals. The study's aims were to determine anti-CDV antibodies in healthy adult dogs within 28 days of vaccination against CDV, and to evaluate factors associated with the presence of pre-vaccination antibodies and with the antibody response to vaccination. Ninety-seven dogs, not vaccinated within 1 year before enrollment, were vaccinated with a modified live CDV vaccine. A measurement of the antibodies was performed before vaccination (day 0), on day 7, and 28 after the vaccination by virus neutralization. A response to vaccination was defined as a ≥4-fold titer increase by day 28. Fisher's exact test was used to determine factors associated with a lack of antibodies and vaccination response. In total, 94.8% of the dogs (92/97; CI 95%: 88.2-98.1) had antibodies (≥10) prior to vaccination. A response to vaccination was not observed in any dog. Five dogs were considered humoral non-responders; these dogs neither had detectable antibodies before, nor developed antibodies after vaccination. Young age (<2 years) was significantly associated with a lack of pre-vaccination antibodies (p = 0.018; OR: 26.825; 95% CI: 1.216-1763.417). In conclusion, necessity of re-vaccination in adult healthy dogs should be debated and regular vaccinations should be replaced by antibody detection.

[Prevention of canine parvovirosis - Part 1: Humoral and cellular immunity]

Canine parvovirosis remains a common and highly infectious disease. Thus, adequate protection is essential for all dogs at any time. In this, humoral immunity plays an essential role. The presence of antibodies in adult dogs suggests immunity against the disease, and nearly all adult dogs possess antibodies (either due to previous vaccination or infection). Meanwhile, worldwide vaccination guidelines recommend measurement of pre-vaccination antibodies instead of regular triennial re-vaccinations in adult dogs. Studies have demonstrated a long lasting duration of immunity against canine parvovirus. Re-vaccination therefore possesses no beneficial effect when dogs already have pre-vaccination antibodies. Thus, when antibodies are present, unnecessary re-vaccinations that potentially cause vaccine-associated adverse events should be avoided. Hemagglutination inhibition and virus neutralization can be performed in specialized laboratories for quantitative antibody titer measurement. Semiquantitative point-of-care (POC) tests for detection of CPV antibodies are available. Since the presence of CPV antibodies in adult dogs that have been vaccinated or previously infected suggests adequate immunity against disease, these POC tests can be a useful tool in practice. They identify dogs that might potentially be unprotected and require re-vaccination during preventive health care appointments. Concerning the POC tests' quality assessment, a high specificity (low number of false positive test results) is considered the most important feature.

Comparison of Four Commercially Available Point-of-Care Tests to Detect Antibodies against Canine Parvovirus in Dogs

Measuring antibodies to evaluate dogs' immunity against canine parvovirus (CPV) is useful to avoid unnecessary re-vaccinations. The study aimed to evaluate the quality and practicability of four point-of-care (POC) tests for detection of anti-CPV antibodies. The sera of 198 client-owned and 43 specific pathogen-free (SPF) dogs were included; virus neutralization was the reference method. Specificity, sensitivity, positive and negative predictive value (PPV and NPV), and overall accuracy (OA) were calculated. Specificity was considered to be the most important indicator for POC test performance. Differences between specificity and sensitivity of POC tests in the sera of all dogs were determined by McNemar, agreement by Cohen's kappa. Prevalence of anti-CPV antibodies in all dogs was 80% (192/241); in the subgroup of client-owned dogs, it was 97% (192/198); and in the subgroup of SPF dogs, it was 0% (0/43). FASTest^® and CanTiCheck^® were easiest to perform. Specificity was highest in the CanTiCheck^® (overall dogs, 98%; client-owned dogs, 83%; SPF dogs, 100%) and the TiterCHEK^® (overall dogs, 96%; client-owned dogs, 67%; SPF dogs, 100%); no significant differences in specificity were observed between the ImmunoComb^®, the TiterCHEK^®, and the CanTiCheck^®. Sensitivity was highest in the FASTest^® (overall dogs, 95%; client-owned dogs, 95%) and the CanTiCheck^® (overall dogs, 80%; client-owned dogs, 80%); sensitivity of the FASTest^® was significantly higher compared to the one of the other three tests (McNemars p-value in each comparison: <0.001). CanTiCheck^® would be the POC test of choice when considering specificity and practicability. However, differences in the number of false positive results between CanTiCheck^®, TiterCHEK^®, and ImmunoComb^® were minimal.

Serosurvey of rabies virus, canine distemper virus, parvovirus, and influenza virus in military working dogs in Korea

Rabies virus (RABV), canine distemper virus (CDV), canine parvovirus type-2 (CPV-2), and canine influenza A virus (CIV) are important contagious pathogens in canine populations. To assess post-vaccination immunity against RABV, CDV and CPV-2, and serological evidence of exposure to influenza A virus in military working dogs (MWDs) in Korea, we tested blood samples of 78 MWDs by fluorescent antibody virus neutralization (FAVN) for RABV, and by commercially available enzyme-linked immunosorbent assay (ELISA) for CDV, CPV-2, and CIV. Korean MWDs had high antibody-positive rates against RABV (97.4%, ≥0.5 IU/ml), CDV (94.8%), and CPV (100%). All dogs tested seronegative (0/78; 0%) for influenza A virus. Two 1-year-old dogs stationed in known rabies outbreak areas (Gangwon and Gyeonggi) exhibited VNA titers below the protective level (0.06 and 0.29 IU/ml, respectively). The breed and sex of MWDs were not significantly associated with antibody titers for RABV, CDV, or CPV; however, age was significantly associated with CPV antibody titers, while region of residence was associated with CDV antibody titer. Taken together, the data presented here provide important insights necessary for post-vaccination management and control of infectious diseases in MWDs.

Serosurvey of rabies virus, canine distemper virus, parvovirus, and influenza virus in military working dogs in Korea

Rabies virus (RABV), canine distemper virus (CDV), canine parvovirus type-2 (CPV-2), and canine influenza A virus (CIV) are important contagious pathogens in canine populations. To assess post-vaccination immunity against RABV, CDV and CPV-2, and serological evidence of exposure to influenza A virus in military working dogs (MWDs) in Korea, we tested blood samples of 78 MWDs by fluorescent antibody virus neutralization (FAVN) for RABV, and by commercially available enzyme-linked immunosorbent assay (ELISA) for CDV, CPV-2, and CIV. Korean MWDs had high antibody-positive rates against RABV (97.4%, ≥0.5 IU/ml), CDV (94.8%), and CPV (100%). All dogs tested seronegative (0/78; 0%) for influenza A virus. Two 1-year-old dogs stationed in known rabies outbreak areas (Gangwon and Gyeonggi) exhibited VNA titers below the protective level (0.06 and 0.29 IU/ml, respectively). The breed and sex of MWDs were not significantly associated with antibody titers for RABV, CDV, or CPV; however, age was significantly associated with CPV antibody titers, while region of residence was associated with CDV antibody titer. Taken together, the data presented here provide important insights necessary for post-vaccination management and control of infectious diseases in MWDs.

Long-lived immunity to canine core vaccine antigens in UK dogs as assessed by an in-practice test kit

OBJECTIVES

To determine the utility of an in-practice test kit to detect protective serum antibody against canine distemper virus, canine adenovirus and canine parvovirus type 2 in a sample of the UK dog population.

MATERIALS AND METHODS

Serum samples from 486 dogs, last vaccinated between less than 1 month and 124 months previously, were tested with the VacciCheck™ test kit for protective antibodies against distemper, adenovirus and parvovirus type 2.

RESULTS

A high proportion of the dogs tested (93·6%) had protective antibody against all three of the core vaccine antigens: 95·7% of the dogs were seropositive against canine distemper virus, 97·3% against canine adenovirus and 98·5% against canine parvovirus type 2. The small number of dogs that were seronegative for one or more of the antigens (n = 31) may have had waning of previous serum antibody or may have been rare genetic non-responders to that specific antigen.

CLINICAL SIGNIFICANCE

UK veterinarians can be reassured that triennial revaccination of adult dogs with core vaccines provides long-lived protective immunity. In-practice serological test kits are a valuable tool for informing decision-making about canine core revaccination.

Seroprevalence of Canine Parvovirus in Dogs in Lusaka District, Zambia

Canine parvovirus (CPV) enteritis is a highly contagious enteric disease of young dogs. Limited studies have been done in Zambia to investigate the prevalence of CPV in dogs. Blood was collected from dogs from three veterinary clinics (clinic samples, n = 174) and one township of Lusaka (field samples, n = 56). Each dog's age, sex, breed, and vaccination status were recorded. A haemagglutination assay using pig erythrocytes and modified live parvovirus vaccine as the antigen was used. Antibodies to CPV were detected in 100% of dogs (unvaccinated or vaccinated). The titres ranged from 160 to 10240 with a median of 1280. Vaccinated dogs had significantly higher antibody titres compared to unvaccinated (p < 0.001). There was a significant difference in titres of clinic samples compared to field samples (p < 0.0001) but not within breed (p = 0.098) or sex (p = 0.572). Multiple regression analysis showed that only age and vaccination status were significant predictors of antibody titres. The presence of antibody in all dogs suggests that the CPV infection is ubiquitous and the disease is endemic, hence the need for research to determine the protection conferred by vaccination and natural exposure to the virus under local conditions.

Prevalence of antibodies to canine parvovirus and reaction to vaccination in client-owned, healthy dogs

The purpose of this population-based cohort study was to assess current prevalence of antibodies to canine parvovirus (CPV) in adult, healthy dogs, including risk factors associated with lack of antibodies, and reaction to revaccination with a modified live vaccine (MLV). One hundred dogs routinely presented for vaccination were included in the study and vaccinated with a single dose of a combined MLV. Information was collected on signalment, origin, environment, vaccination history and side effects. Prevaccination and postvaccination antibodies were detected by haemagglutination inhibition. Univariate analysis, followed by multivariate logistic regression, was used to investigate association between different variables and presence of antibodies as well as titre increase. Protective CPV antibodies were present in 86.0 per cent of dogs. Intervals of more than four years since the last vaccination and rare contacts with other dogs were determined as main risk factors for the absence of antibodies. An increase in titres only occurred in 17.0 per cent of dogs. Dogs without protective titres before vaccination or with bodyweight <10 kg were more likely to have an adequate titre increase. Based on these findings, antibody status should be determined instead of periodic vaccinations to ensure reliable protection without unnecessary vaccinations in adult dogs.

Survey of veterinary surgeons on the introduction of serological testing to assess revaccination requirements

Despite the discussion of the use of serological testing in canine vaccination protocols, no study has been published that investigates the opinions of the veterinary profession regarding the use of the test to assess revaccination requirements in dogs. This paper presents the results of a study designed to fill this research gap which was completed in 2009. Veterinary surgeons were asked to complete a questionnaire on different aspects of canine vaccination and the introduction of serological testing to determine revaccination requirements. Of the 448 questionnaires distributed, 243 replies were received (54.2 per cent) and of these, a significant majority (169/243; 69.5 per cent) of respondents would consider introducing serological testing. An average of 53.5 per cent of respondents practised tri-annual revaccination for the core diseases. A significant number of respondents (86/140; 61 per cent) who placed low importance on vaccine overload would consider introducing serological testing into canine vaccination programmes (P=0.002).

Duration of immunity induced by companion animal vaccines

Concerns about possible adverse effects from annual vaccination have prompted the reanalysis of vaccine protocols for cats and dogs. In the last decade, several veterinary advisory groups have published protocols that recommend extended revaccination intervals for certain ‘core’ vaccines. In addition, practicing veterinarians have been asked to consider vaccination as an individualized medical procedure, based on an analysis of risks and benefits for each vaccine in an individual animal. The calls for extended revaccination intervals prompted considerable debate in USA and internationally. Areas of concern include the amount of evidence to support prolonged immunity from various vaccines, the risk of poor responses in individual animals and the possible effects on population immunity. This review examines how the duration of immunity (DOI) to a vaccine is established in animals and humans. It reviews factors that can affect the DOI in an individual animal, including the types of immune defenses stimulated by the pathogen, and the vaccine, host factors such as age and the level of exposure to the pathogen. In addition, it examines DOI studies that were published for canine and feline core vaccines.