Rapid Fluorescent Focus Inhibition Test Research Articles

Rabies Virus-Neutralizing Antibodies in Free-Ranging Invasive Wild Boars (Sus scrofa) from Brazil.

Rabies, one of the most lethal global zoonoses, affects all mammals. It remains circulating worldwide in sylvatic cycles through terrestrial and airborne reservoirs, and in Brazil, bats are currently the main reservoirs and source of transmission. Wild boars, an important invasive alien species in Brazil, are a proven food source for hematophagous bats and may participate in the Brazilian sylvatic cycle of rabies. We evaluated the presence of this pathogen in hunted wild boars from the São Paulo state using histopathology, the direct fluorescent antibody test (DFA), viral isolation in cell culture (VICC), the rapid fluorescent focus inhibition test (RFFIT), and quantitative reverse transcription polymerase chain reaction (RT-qPCR). The results of histopathological, DFA, VICC, and RT-qPCR analysis were negative for all samples; seven serum samples tested positive in the RFFIT, and titers ranged from 0.13 IU/mL to 0.5 IU/mL. The presence of rabies virus-neutralizing antibodies in the studied wild boars suggests the circulation of the virus in these animals. Educative actions directed at hunters should include information on the prevention of this important zoonosis.

Immunogenicity and Safety of a Purified Vero Rabies Vaccine - Serum Free, Compared With Two Licensed Vaccines, in a Simulated Rabies Post-Exposure Regimen in Healthy Adults in France: A Randomized Controlled Phase III Trial.

A next-generation Vero cell rabies vaccine (PVRV-NG2) was developed using the same Pitman-Moore strain as in the licensed purified Vero cell vaccine (PVRV; Verorab®) and the human diploid cell vaccine (HDCV; Imovax Rabies®). This dual-center, modified double-blind, phase III study in France evaluated immunogenic non-inferiority and safety of PVRV-NG2 with and without concomitant intramuscular human rabies immunoglobulin (HRIG), compared with PVRV+HRIG and HDCV+HRIG, in a simulated post-exposure prophylaxis (PEP) regimen. Healthy adults ≥18 years old (N=640) were randomized 3:1:1:1 to receive PVRV-NG2+HRIG, PVRV+HRIG, HDCV+HRIG, or PVRV-NG2 alone (administered as single vaccine injections on days [D] 0, 3, 7, 14, and 28, with HRIG administered on D0 in applicable groups). Rabies virus neutralizing antibodies (RVNA titers) were assessed pre- (D0) and post-vaccination (D14, D28, and D42) using the rapid fluorescent focus inhibition test. Non-inferiority, based on the proportion of participants achieving RVNA titers ≥0.5 IU/mL (primary objective), was demonstrated if the lower limit of the 95% CI of the difference in proportions between PVRV-NG2+HRIG and PVRV+HRIG/HDCV+HRIG was >-5% at D28. Safety was assessed up to 6 months after the last injection. The non-inferiority of PVRV-NG2+HRIG, compared with PVRV+HRIG and HDCV+HRIG, was demonstrated. Nearly all participants (99.6%, PVRV-NG2+HRIG; 100%, PVRV+HRIG; 98.7%, HDCV+HRIG; 100%, PVRV-NG2 alone) achieved RVNA titers ≥0.5 IU/mL at D28. Geometric mean titers were similar between groups with concomitant HRIG administration at all time points. Safety profiles were similar between PVRV-NG2 and comparator vaccines. In a simulated PEP setting, PVRV-NG2+HRIG showed comparable immunogenicity and safety to current standard-of-care vaccines. NCT03965962.

Long-term immunity induced by SPBN GASGAS in orally vaccinated dogs is non-inferior to inactivated rabies vaccines

In a long-term immunogenicity study (1100 days post vaccination) in local Thai dogs the immune response of the oral rabies vaccine SPBN GASGAS was compared to those elicited by a commercial inactivated vaccine using immunobridging. Based on the detection of rabies virus binding (rVBA) and rabies virus neutralizing antibodies (rVNA) as measured by ELISA and Rapid Fluorescent Focus Inhibition Test (RFFIT) the long-term immune response in dogs vaccinated orally with the SPBNA GASGAS strain of rabies vaccine in a bait was non-inferior to a conventional inactivated rabies vaccine. The outcome of this study supports extending the originally claimed duration of immunity (DOI) of SPBN GASGAS after oral vaccination for dogs from 6 to 30 months.

Safety and immunogenicity of three dose levels of an investigational, highly purified Vero cell rabies vaccine: A randomized, controlled, observer-blinded, Phase II study with a simulated post-exposure regimen in healthy adults

ABSTRACT A serum-free, highly purified rabies vaccine produced in Vero cells is under development. The initial formulation, PVRV-NG, was evaluated in five Phase II studies and subsequently reformulated (PVRV-NG2). This multicenter, observer-blinded Phase II study investigated the safety and immune response of three different doses (antigen content) of PVRV-NG2 versus a licensed human diploid cell rabies vaccine (HDCV; Imovax rabies®). Healthy adults (N = 320) were randomized to receive PVRV-NG2 (low, medium, or high dose), PVRV-NG, or HDCV (2:2:2:1:1 ratio), according to a five-dose Essen simulated post-exposure regimen (Days [D] 0, 3, 7, 14, and 28). All participants received human rabies immunoglobulin intramuscularly on D0. Immunogenicity was assessed at D0, 14, 28, 42, and 6 months after the final injection using the rapid fluorescent focus inhibition test. Seroconversion rates were calculated as the percentage of participants achieving rabies virus neutralizing antibody titers ≥0.5 IU/mL. All analyses were descriptive. At each timepoint, geometric mean titers (GMTs) increased with antigen content (measured using an enzyme-linked immunosorbent assay). High-dose PVRV-NG2 GMTs were the highest at all timepoints, medium-dose PVRV-NG2 GMTs were similar to those with HDCV, and low-dose PVRV-NG2 GMTs were similar to PVRV-NG. The safety profile of PVRV-NG2 was comparable to PVRV-NG; however, fewer injection site reactions were reported with PVRV-NG2 or PVRV-NG (range 36.7–47.5%) than with HDCV (61.5%). This study demonstrated a dose–effect of antigen content at all timepoints. As post-exposure prophylaxis, the safety and immunogenicity profiles of the high-dose PVRV-NG2 group compared favorably with HDCV. Clinicaltrials.gov number: NCT03145766.

Construction and development of new rabies virus vectors carrying enhanced green fluorescent protein

Aim: Rabies is one of the most lethal viral diseases. This study developed a recombinant rabies virus, PVEGFP, expressing an EGFP protein based on PV strain to be applied in virus-neutralizing antibody (VNA) titration methods. Methods: The EGFP gene was inserted into the PVMCS strain, a previously discussed recombinant virus. The recombinant virus was applied in the rapid fluorescent focus inhibition test (RFFIT) VNA titration method, and six vaccinated persons were studied for validation. Results: The recombinant rabies strain showed similar propagation properties to its ancestry strain, PVMCS. It could also measure VNA titers in the RFFIT method not significantly different from those acquired using the CVS-11 virus. Conclusion: Utilizing the PVEGFP strain in the RFFIT method can produce rapid, reliable and affordable results.

Evaluation of an iELISA for detection and quantification of rabies antibodies in domestic dog sera

Many rabies endemic-countries have recognized rabies as a public health problem that can be eliminated. As a result, some countries have started implementing small-scale vaccination programs with the aim of scaling them up. Post-vaccination serological monitoring is crucial to assess the efficacy of these programs. The recommended serological tests, the rapid fluorescent focus inhibition test, and the fluorescent antibody virus neutralization (FAVN) are accurate; however, the procedures require considerable expertise and must be carried out in high containment facilities, which are often not available in rabies endemic countries. Given these constraints, enzyme linked immunosorbent assays (ELISAs) have been considered as alternative methods to neutralization tests. This is the first study to evaluate, under field conditions, the performance of the commercial rabies indirect-ELISA (iELISA), the PlateliaTM Rabies II kit ad usum Veterinarium kit, using sera from domestic dogs. Serum samples were collected from two groups of community dogs in northern Tanzania: i) dogs with no history of vaccination against rabies (n = 100) and ii) dogs vaccinated with the Nobivac Canine Rabies® vaccine (n = 101) four weeks previously. When compared to the gold standard FAVN test, the iELISA was found to be 99% specific and 98% sensitive and there was a significant correlation between the two tests (p < 0.001, r = 0.92). Given these findings, we conclude that the PlateliaTM Rabies II kit ad usum Veterinarium can be considered a valuable tool for the rapid assessment of vaccination status of animals in vaccination programs.

Assessment of Immune Responses to Rabies Vaccination in Free-Ranging Dogs in Bengaluru, India.

Rabies is a fatal encephalomyelitis mainly transmitted to humans and other animals by rabid dog bites. Hence, vaccination programs are being instituted for the control of rabies in dogs. Though stray dogs have been vaccinated for years under various programs initiated for control of the disease, the effectiveness of these programs can be ascertained only by assessing the immunity of these dogs. With this in view, a study was conducted to assess the effectiveness of the ongoing mass dog vaccination (MDV) program by the Bengaluru City Municipal Corporation, Bengaluru, India. Whole blood and serum samples (n = 260) from vaccinated stray dogs in 26 wards of 8 corporation zones were tested by rapid fluorescent focus inhibition test (RFFIT) as well as an in-house quantitative indirect enzyme-linked immunosorbent assay (iELISA) for a humoral response and by interferon-gamma (IFN-γ) ELISA for a cellular response. As determined by the cut-off value of 0.5 IU/mL of serum, 71% and 87% of the samples from vaccinated dogs revealed adequate levels of antibodies presumed to confer protection by RFFIT and iELISA, respectively. The sensitivity and specificity of the iELISA were 100% and 63.3%, respectively. The IFN-γ ELISA revealed adequate cellular response in 50% of the samples. The quantitative iELISA was found to be useful in large-scale seromonitoring of MDV programs to aid in the elimination of dog-mediated rabies.

Comparative Evaluation of Intradermal vis-à-vis Intramuscular Pre-Exposure Prophylactic Vaccination against Rabies in Cattle.

Rabies is a progressively fatal viral disease affecting a wide variety of warm-blooded animals and human beings. With cattle being major part of Indian livestock population, rabies can result in significant financial losses. Immunization of livestock vulnerable to exposure is the best way to control rabies. The present study was undertaken to investigate the efficacy of a rabies pre-exposure prophylactic vaccine administered through different routes and to sequentially monitor the levels of rabies virus-neutralizing antibody (RVNA) titers in cattle. Thirty cattle were divided into five groups of six animals each. Group I and III animals were immunized with 1 mL and 0.2 mL of rabies vaccine through intramuscular (IM) and intradermal (ID) routes, respectively, on day 0, with a booster dose on day 21; Group II and IV animals were immunized with 1 mL and 0.2 mL of rabies vaccine, respectively, without the booster dose; unvaccinated animals served as a control (Group V). Serum samples were collected on days 0, 14, 28, and 90 to estimate RVNA titers using the rapid fluorescent focus inhibition test (RFFIT). The titers were above an adequate level (≥0.5 IU/mL) on day 14 and maintained up to 90 days in all animals administered the rabies vaccine through the IM and ID route with or without a booster dose. The study indicated that both routes of vaccination are safe and effective in providing protection against rabies. Hence, both routes can be considered for pre-exposure prophylaxis. However, the ID route proved to be more economical due to its dose-sparing effect.

Validation of Adapted Neutralization Assays Developed to Discriminate Anti-Rabies Virus Activity of Two Different Anti-Rabies Virus Monoclonal Antibodies Administered as a Combination

Assessment of rabies virus (RABV) neutralizing antibodies in subjects vaccinated or injected with anti-RABV immunoglobulins is central in determination of rabies protection. The rapid fluorescent focus inhibition test (RFFIT) is used for assessment of anti-RABV activity in serum. The current anti-RABV polyclonal preparations on the market pose difficulties in production and vary in quality. RABV neutralizing monoclonal antibodies (MAbs) are being evaluated as replacements. Different anti-RABV MAbs may neutralize different RABV isolates, thus two or more MAbs directed against different epitopes on the RABV glycoprotein are needed. It is therefore important to ensure neutralizing activity against all RABV isolates in sera of subjects injected with an anti-RABV MAb product consisting of two or more MAbs. The RFFIT, utilizing CVS-11 as challenge virus, cannot discriminate between the activities of different anti-RABV MAbs. We developed and validated two RFFIT methods enabling specific assessment of two different anti-RABV MAbs (CR57 and CR4098) in using two mutant CVS-11 strains resistant to either CR57 or CR4098 neutralization. The validation results demonstrate that both RFFIT assays using MAb resistant RABV are precise, accurate, linear, specific, and stable within the linear range of 0.025 IU/mL to 1.0 IU/mL. This method design can, therefore, be used to determine MAb specific anti-RABV activity in human serum samples.

Quantification and evaluation of rabies virusneutralizing antibody titers by modified rapid fluorescent focus inhibition test

Quantification and evaluation of rabies virusneutralizing antibody titers by modified rapid fluorescent focus inhibition test

Survival of 21 Dogs after Post-exposure Prophylaxis using Intra-dermal Rabies Vaccine in the Pre-scapular Region and Emergency Use of Expired Equine Rabies Immunoglobulin for Local Wound Infiltration in Victims of a Rabid Dog Bite using One Health Approach

Rabies is a 100% fatal zoonotic disease and is preventable through timely and adequate Post-Exposure Prophylaxis (PEP). World Organization for Animal Health (WOAH) haven’t issued any guidelines for PEP for rabies in animals, still in certain Indian states like Himachal Pradesh (HP) PEP regimen with active immunization on 0,3,7,14 and 28 days mostly by Intramuscular Rabies Vaccine (IMRV) is being followed. Recently in Rampur Bushahar, a suspected rabid dog later laboratory confirmed had bitten 21 dogs, 2 cows, and 2 men. We employed PEP in animals using Raksharab vaccine intra-dermally (IDRV) (0.2 ml, pre-scapular region) on days 0, 3,7,14, and 28 along with only local wound infiltration of eRIG in 8 out of 11 bitten dogs with Category III exposure. Furthermore, 3 noncooperative dogs with Category III exposure were given IMRV (1ml) on day 0,3,7,14,28 with only wound infiltration of eRIG. 2 Cows were administered 0.2 ml IDRV in the skin at the middle of the neck with only wound infiltration of eRIG. Human bite victims also received 0.1 ml IDRV at 2 sites in the deltoid region on days 0,3, and 7 along with wound infiltration of eRIG at the nearby health center. Serum samples were collected for Rapid Fluorescent Focus Inhibition Test (RFFIT) for estimation of Rabies Vaccine Neutralizing Antibody (RVNA) titer after day 14 for 8 dogs, 2 cows, and human bite victims, and all had RVNA titer &gt;0.5 IU/ml on day 14 except one in IMRV group. None of the bitten victims had clinical manifestations of rabies even after 1 year of follow-up. This indicates wound infiltration with eRIG along with the vaccine could be a life-saving protocol. Also using expired eRIG in emergencies was safe and life saving in animals. Expired eRIG used was later tested and was found to be potent.

Intravitam Diagnosis of Rabies in Patients with Acute Encephalitis: A Study of Two Cases.

Rabies is one of the oldest known zoonotic diseases. Rhabdovirus, an RNA virus belonging to the genus Lyssavirus and family Rhabdoviridae, causes rabies. Rabies diagnosis is challenging as the rabies virus remains confined to neurons after the initial animal bite. It largely remains immune-evasive until the infection reaches the central nervous system. The bottleneck in rabies diagnosis remains the non-availability of technical expertise and failure to collect an appropriate sample. The laboratory confirmation of rabies in both antemortem and postmortem samples is important. The samples were tested for anti-rabies antibodies using quantitative ELISA. In this report, two case studies are presented to demonstrate the suitability of ELISA for the intra vitam diagnosis of rabies using cerebrospinal fluid (CSF) as a diagnostic sample. The interpretation of serology results for both vaccinated and unvaccinated individuals has been discussed in detail, which has helped to confirm the antemortem diagnosis of rabies. In this report, we observed that ELISA can be a viable alternative for anti-rabies antibody detection in CSF and can be used as a viable alternative to more technically challenging tests, such as Rapid Fluorescent Focus Inhibition Test (RFFFIT) and Immunofluorescence Assays (IFA).

A simulated, randomized study on the safety and immunogenicity of three consecutive commercial-scale batches of the CTN-1V strain human rabies vaccine to verify the inter-batch consistency

ABSTRACT In this study, we sought to evaluate the inter-batch consistency and safety of the CTN-1 V human rabies vaccine (Vero cells). A total of 594 healthy participants aged 10–60 years were enrolled from Mianzhu, Sichuan Province, and randomized into three batch groups to receive vaccination via the Essen Regimen, that is, a single dose on days 0, 3, 7, 14, and 28 in the deltoid muscle of the upper arm. The serum antibody geometric mean concentration (GMC) and positive conversion rate of each group were determined using a rapid fluorescence focus inhibition test (RFFIT) before the first-dose immunization, 14 d after the first-dose immunization, and 14 d and 12 mo after full immunization. Adverse events (AEs) 30 min and 30 d after immunization were observed in each group. There were 322 cases of AEs during the observation period, with an overall incidence of 54.4%. The incidences of AEs in groups A, B, and C were 57.4%, 51.5%, and 54.3%, respectively. There were no significant differences among the groups (P > .05). Moreover, there were no significant differences (P > .05) in the serum GMC or antibody-positive conversion rate between any two groups at any time point. The bilateral 95% confidence interval of the GMC ratio between any two groups 14 d after the first-dose immunization was within the range of 0.67–1.50. This study shows that the CTN-1 V human rabies vaccine (Vero cells) has reliable safety and stable immunogenicity between batches.

Establishment and clinical validation of an in-cell-ELISA-based assay for the rapid quantification of Rabies lyssavirus neutralizing antibodies.

Neutralizing antibodies (nAbs) prevent the entry of viruses into permissive cells. Since nAbs represent correlates of protection against the Rabies lyssavirus, the presence of sufficient nAbs indicates effective vaccination. Accordingly, Rabies lyssavirus-specific nAb titers need to be determined in routine diagnostics to identify individuals being at risk of Rabies lyssavirus infections due to insufficient immunity. The current gold standard for the quantification of Rabies lyssavirus-specific nAbs is the rapid fluorescent focus inhibition test (RFFIT). However, RFFITs are expensive and labor-intensive since multiple microplate wells must be evaluated one-by-one by trained personnel through microscopic inspection, which limits the number of samples that can be processed. To overcome this disadvantage, we established a novel assay for Rabies lyssavirus-specific nAbs relying on an in-cell-ELISA (icELISA)-based neutralization test (icNT). The icNT differs from the RFFIT in the readout phase, and can be automatically quantified in minutes using broadly available microplate readers. During the establishment, icNT parameters such as antibody concentrations, permeabilization procedures, blocking reagents, infectious doses, and the duration of infection were optimized. Afterwards, a dose-dependent detection of Rabies lyssavirus neutralization was demonstrated using the WHO Standard Rabies Immunoglobulin reference. A panel of 200 sera with known RFFIT titers revealed very good sensitivity and specificity of the icNT. Furthermore, the icNT showed very good intra- and inter-assay precision. By recognizing Rabies lyssavirus-specific antigens, the assay can be applied immediately to automatically quantify the concentration of Rabies lyssavirus nAbs in routine diagnostics or for various basic research questions such as screening for antiviral compounds.

Seroprevalence to Rabies Virus in Wildlife in Brazil.

Serum samples of 638 free-ranging wild mammals from São Paulo state, Brazil, were tested for neutralizing antibodies against rabies virus by the rapid fluorescent focus inhibition test. Overall seroprevalence was 1.7% among 24 species surveyed, with individuals of six species having positive results indicating exposure to rabies virus.

A Comparative Evaluation of the Estimation of Rabies Virus Antibodies among Free-Roaming, Vaccinated Dogs in Bengaluru, India.

Vaccination is the practical solution for the prevention of rabies in dogs. Assessment of the immunogenicity of vaccination includes estimation of specific rabies virus neutralizing antibodies (VNA) in the target species. We undertook a study to estimate the levels of VNA in free-roaming dogs with a history of rabies vaccination in Bengaluru city, India. We compared the rapid fluorescent focus inhibition test (RFFIT) and an in-house quantitative indirect ELISA (iELISA). The study area comprised the jurisdiction of Bruhat Bengaluru Mahanagara Palike (BBMP), the Bengaluru civic body. The BBMP, along with several non-government organizations (NGO), were conducting a trap- neuter- vaccinate- release program for the prevention of dog rabies. Serum samples were collected from 250 free-roaming dogs from representative regions of BBMP, of which 125 had a VNA titre of 0.5 IU or more by the RFFIT. Furthermore, 126 dogs showed percent positivity values (PP values) more than the cut off PP value of 57.1 by the iELISA, accounting for 50.4% of satisfactory post-vaccinal serum conversion. The sensitivity and specificity of the iELISA was 94.4% and 95.2%, respectively. Based on these data, a quantitative iELISA may be a complementary tool for sero-monitoring immune responses of free-ranging animals after rabies vaccination.

Serological survey of lyssaviruses in synanthropic bats and human exposure to bats in Slovakia.

Bats are considered natural reservoirs for lyssaviruses. A total of 17 out of 19 known lyssaviruses circulate in bat populations. Lyssaviruses cause rabies in animals and humans. The transmission of lyssaviruses from European bats to terrestrial animals and humans is rare, but the risk of infection still exists even in developed countries. Slovakia is currently a rabies-free country. The aim of the study was to assess the potential circulation of EBLV-1 in synanthropic bats present in human inhabited buildings, and to give an overview of human exposure to bats. A passive serological survey targeted the prevalence of antibodies to bat lyssaviruses in synanthropic bats between 2009 - 2019. A total of 598 bats of the species Pipistrellus pipistrellus, Pipistrellus pygmaeus, Eptesicus serotinus, Nyctalus noctula and Vespertilio murinus were captured in buildings mainly in Eastern Slovakia, and examined by the rapid fluorescent focus inhibition test (RFFIT). Lyssavirus-specific antibodies were detected in 2 (0.3%) of the 598 examined bats. Additionally, brain tissues of bats found dead were examined using the standard fluorescent antibody test (FAT) with negative results. An overview of available data on human exposure to bats recorded in Slovakia from 2007 - 2019 is also included. The study confirmed the presence of lyssavirus antibodies in synanthropic bats in Slovakia, suggesting the active circulation of bat lyssaviruses in bat populations exploiting human buildings. Although the seroprevalence was found to be extremely low, the results show that any case of human exposure to bats must be treated with caution in order to protect public health.

Evaluation of dog vaccination schemes against rabies in Kinshasa, Democratic Republic of the Congo

The traditional rabies control strategy based on annual mass vaccination of dogs appears to be costly and cumbersome. Given the existence of different risk zones for rabies transmission, the present study aimed at proposing risk-based vaccination schemes by considering canine population dynamics as well as vaccine efficacy and duration of immunity (DOI). The capital of the Democratic Republic of the Congo (RDC), Kinshasa, was chosen as study site. The turnover rate of dogs was used to assess their population dynamics in two low-roaming (<25 % of dogs are roaming) and in two high-roaming zones (>75 % of dogs are roaming). The sero-conversion rate was assessed in response to primo-vaccination in three age groups: 24 puppies (≤3months), 37 juveniles (4–12 months) and 22 adult dogs. The DOI was evaluated serologically by revaccinating dogs previously vaccinated since 1–2 years (n = 31), 2–3 years (n = 12) or 3–7.5 years (n = 4). Rapid Fluorescent Focus Inhibition Test was used to quantify antibodies. These data were used to implement vaccination outcome models.The turnover rate was twice as high in high-roaming zones (36 %) as that in lowroaming zones (17 %). Irrespective of roaming level, 75 % of dogs were less than 3 years old. The vaccine was equally effective in puppies (96 %), juvenile (97 %) and adult dogs (100 %, p = 0.24). The vaccine was effective in 93 % (11/12) of puppies without pre-vaccinal protective titers (≥0.5 IU/mL). The anamnestic response was strong within 5–8 days upon the booster vaccination, in 96 % (45/47) of dogs reported vaccinated 1–7.5 years before. This suggests that the vaccine provided a long-term protection (≥3 years) which is likely to occur in 75 % of dogs in Kinshasa.Hypothesizing a vaccination stop, the vaccination outcome model allowed to estimate the time point after which vaccination coverage would drop below 40 % in function of dog population turnover rate. The systematic vaccination of puppies as well as annual vaccination of dogs aged between 3 and 15 months or annual vaccination of all unvaccinated dogs aged more than 3 months of age appeared as valuable alternative to systematic annual mass vaccination.In conclusion, this study developed a vaccination outcome model pointing out the impact of dog population dynamics and of effective duration of immunity. It appears as a promising tool for designing cost-effective rabies vaccination campaigns

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

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). 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. 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. 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. 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.

Immunogenicity of the Oral Rabies Vaccine Strain SPBN GASGAS in Dogs Under Field Settings in Namibia.

Dog-mediated rabies is endemic throughout Africa. While free-roaming dogs that play a crucial role in rabies transmission are often inaccessible for parenteral vaccination during mass dog vaccination campaigns, oral rabies vaccination (ORV) is considered to be a promising alternative to increase vaccination coverage in these hard-to-reach dogs. The acceptance of ORV as an efficient supplementary tool is still low, not least because of limited immunogenicity and field trial data in local dogs. In this study, the immunogenicity of the highly attenuated 3rd-generation oral rabies vaccine strain SPBN GASGAS in local free-roaming dogs from Namibia was assessed by determining the immune response in terms of seroconversion for up to 56 days post-vaccination. At two study sites, free-roaming dogs were vaccinated by administering the vaccine either by direct oral administration or via a vaccine-loaded egg bait. Pre- and post-vaccination blood samples were tested for rabies virus neutralizing as well as binding antibodies using standard serological assays. A multiple logistic regression (MLR) analysis was performed to determine a possible influence of study area, vaccination method, and vaccine dose on the seroconversion rate obtained. About 78% of the dogs vaccinated by the oral route seroconverted (enzyme-linked immunosorbent assay, ELISA), though the seroconversion as determined by a rapid fluorescence focus inhibition test (RFFIT) was much lower. None of the factors examined had a significant effect on the seroconversion rate. This study confirms the immunogenicity of the vaccine strain SPBN GASGAS and the potential utility of ORV for the control of dog-mediated rabies in African dogs.