Evaluation of Bait Acceptance and Immune Response in Local Dogs during an Oral Rabies Vaccination Field Study in Morocco.

The objective of this study was to evaluate the bait preference of three selected bait types by local dogs and the induced immunogenicity of the oral rabies vaccine strain SPBN GASGAS in Morocco. The vaccine strain, combined with different bait types, has been tested in many different settings, but not yet in northern Africa. Overall, bait consumption and preference were similar in other studies using the same materials (bait type and sachet). The intestine bait had the highest acceptance rate (97.6%, 95%CI: 87.4-99.9), followed by the egg bait (83.0%, 95%CI: 69.2-92.4). Only 52% (95%CI: 37.4-66.3) of the dogs showed an interest in the fish meal bait. However, considering the successful release of the contents of the sachet (blue-dyed water) into the oral cavity, the egg bait (65.7%, 95%CI: 47.8-80.9) scored better than the intestine bait (51.7%, 95%CI: 32.5-70.6). The dogs selected for the immunogenicity study were offered the egg bait containing a sachet filled with SPBN GASGAS (3.0 mL, 107.5 FFU/mL) or were given the same dose by direct oral administration (d.o.a.). In addition, several dogs were vaccinated by the parenteral route (s.c.) using a commercially available inactivated rabies vaccine. Unfortunately, due to the COVID-19 pandemic and subsequent travel restrictions, it was not possible to collect blood samples directly after vaccination. The blood samples were collected pre-vaccination and on five occasions between 450 and 1088 days post vaccination. The seroconversion rate, as determined for rabies-virus-neutralizing antibodies by the FAVN test, was significantly lower than that found for binding antibodies, as determined by ELISA, for all blood samples collected post vaccination. No treatment effect (bait, d.o.a., s.c.) could be seen in the seroconversion rate. At 15 months post vaccination, 84.2% of the dogs offered vaccine bait still tested sero-positive in ELISA. Only after 3 years was a clear drop in the seroconversion rate observed in all three treatment groups. This study confirms the long-term immunogenicity of the oral rabies vaccine SPBN GASGAS in dogs under field conditions.

Pathogenicity of field strain of fowl aviadenovirus serotype 11 isolated from chickens with inclusion body hepatitis in Morocco.

Outbreaks of inclusion body hepatitis have emerged in Morocco since 2013 and has resulted in significant economic losses to poultry farms. Three isolates of the causative virus, Fowl adenonovirus (FAdV)were characterized from chickens with IBH, but their pathogenicity has never been investigated. In this work, the pathogenicity of an isolate FAdV 11 (MOR300315 strain) was evaluated by inoculating a group of 40 SPF chickens at 3 days of age by oral route. A group of 40 chicks injected with phosphate-buffered saline solution was used as a control group. The infected chickens showed decreased weight gain from 3dpi. Necropsy displayed pallor and enlargement in liver, swelling and slight hemorrhage in kidney and spleen at 6 dpi. Histopathological changes were mainly characterized by severe and extensive hepatic necrosis associated with the presence of basophilic intra-nuclear inclusion bodies within hepatocytes. The FAdV was reisolated in chicken embryo fibroblast cell culture from liver tissue homogenate of infected chicken from 3 to 6 dpi. Viral DNA was detected by PCR in liver, kidney, spleen and cloacal swabs from 3 to 13 dpi. Antibody response against inoculated FAdV was appeared from 9 dpi. These results confirmed that the FAdV 11 strain is pathogenic in chicken. This study is the first experimental infection of FAdV 11 in chicken in Morocco, which increase our understanding of its pathogenicity in chickens and indicate that preventive measures against FAdV infection in poultry farms should be implemented in Morocco.

Immunity Elicited by a Turkey Herpesvirus-Vectored Newcastle Disease Vaccine in Turkey Against Challenge With a Recent Genotype IV Newcastle Disease Virus Field Strain.

Newcastle disease (ND) is still a major poultry disease worldwide. Vaccination remains the principal method of controlling ND in endemic countries. Various vaccination strategies, including the use of recently developed recombinant vaccines, have been used to control it. Recombinant vaccines that use the herpesvirus of turkey (HVT) as a vector to express one of the key antigens of Newcastle disease virus (NDV) have been developed to overcome some of the drawbacks related to the use of conventional vaccines. HVT as a vector appears to have unique beneficial characteristics: it is extremely safe, it is not affected by the presence of maternally derived antibodies, and therefore can be applied in the hatchery either in ovo or to day-old chicks. Due to its persistence in the bird, the HVT vector can be expected to induce life-long immune stimulation. In the present study, the efficacy of an HVT-based vector vaccine expressing the F gene of NDV (rHVT-F) was tested against a velogenic genotype IV NDV challenge in commercial turkeys with high levels of maternal antibodies (8.7 ± 0.8 log2 hemagglutination inhibition titer). The birds were vaccinated on the day of hatch by the subcutaneous route. Development of a humoral immune response to vaccination was detectable from 4 weeks of age by ELISA. The challenge strain used represents recent NDV genotype IV field strains from Morocco. Challenge with this strain induced ND-specific clinical signs and stunting without subsequent mortality in the non-vaccinated birds, whereas the vaccinated turkey poults showed protection as early as 3 weeks of age based on lack of clinical signs, better body weight gain, and reduction of challenge virus shedding. This is the first reported efficacy study of an HVT-vectored ND vaccine against a velogenic NDV challenge in commercial turkeys.

A Century Spent Combating Rabies in Morocco (1911-2015): How Much Longer?

Rabies has no known beginning in Morocco and to date, government control efforts and plans fail to eradicate the disease. A review and analysis of available epidemiological data are crucial to learn lessons from the past and to propose effective actions. Legally, animal rabies is a notifiable disease since 1913 and legislation has been updated periodically since. Dogs have always been considered as both the disease's vector and reservoir, while cattle, other herbivores, and humans are victims. Animal rabies cases evolution from 1942 to 2015 is characterized by ascending phase then decreasing one following structured rabies control plan implementation in 1980s. Indeed, from 1986 to 2010, three rabies control plans have been conducted based on free of charge rabies vaccination of owned dogs through mass campaigns. The geographical distribution of rabies is stable over the years with highest cases number in rich rural areas and around cities. Human rabies cases are decreasing over the time (1976-2015) thanks to the opening of new antirabic treatment centers in the last decade which permit the administration of more PEPs. After a century of rabies control, Morocco registered an average of 301 animal cases and 21 human cases annually for the last decade (2005-2015). Few reasons led to those limited results. The lack in law enforcement and, moreover, the fact that the law do not take into account responsible dog ownership aspect are of importance. Lack of dog population knowledge and management and intersectoral coordination deficiency are additional failure reasons. The gathered data will help to build a new strategy with a focus on a "One Health" approach. Dog population ecology parameters' study is of primary importance. We estimated dog population to be 2.8 million dogs based on human:dog ratio. Enhancing vaccination coverage of dog population is feasible by combining parenteral vaccination and complementary oral vaccination. Updating legislation by inclusion of responsible dog ownership and law enforcement are crucial. Over the last century, Morocco registered a slow decreasing tendency in the number of animal and human rabies cases. Urgent strategy need to be implemented because rabies elimination is an achievable goal in Morocco.

Immunogenicity and efficacy of Rabivac vaccine for animal rabies control in Morocco.

PURPOSE: To fight animal rabies, Moroccan veterinary authorities organize annual dog mass vaccination campaigns using Rabivac vaccine, an inactivated adjuvanted cell culture veterinary rabies vaccine. Two experiments were undertaken to assess the efficacy and immunogenicity of Rabivac. MATERIALS AND METHODS: The first experiment involved 13 caged dogs (8 vaccinated and 5 negative controls). Dogs were bled at day 0 (D0) and at days D7, D14, D21, D28, D35, D49, D56, D64, D70, D77, D84, D91, D98, D105, D112, and D119 post-vaccination. At D121, a virulent challenge was performed. After 70 days monitoring period, seven out of eight vaccinated dogs survived the challenge (one dog succumbed to a mesenteric torsion accident) and four out of five controls succumbed. All vaccinated dogs seroconverted and the control dogs remained negative. The second experiment consisted in a field study involving 919 owned dogs randomly selected in eight Moroccan districts located in different parts of the country. The dogs were identified and vaccinated by the parenteral route and bled on the vaccination day (D0) and on D30. RESULTS: Ninety-two percent of dogs developed a positive rabies virus neutralizing antibody response to vaccination and 24% were positive at D0, suggesting that dogs were previously vaccinated. The increase in rabies antibody titers was highly significant in all districts. No significant difference seemed occurring between the geographical status (rural, semiurban, or urban) of the districts on the results obtained. CONCLUSION: Rabivac is efficacious both in experimental and field conditions. This supports its use in dog mass vaccination campaigns.

First trials of oral vaccination with rabies SAG2 dog baits in Morocco.

PURPOSE: Canine rabies is a serious health problem in Morocco and about 22 human deaths are reported yearly. Following the World Health Organization (WHO) recommendations, Moroccan authorities evaluated oral rabies vaccine baits specially designed for dogs. MATERIALS AND METHODS: The study was performed in Tiflet area. The vaccine strain was SAG2, a modified live oral rabies vaccine strain. Each bait contained an aluminium/PVC capsule filled with a liquid. Two kinds of baits were used: placebo baits containing methylene blue as a topical marker and vaccine baits containing vaccine suspension. The study was performed according to recommended WHO strategies, i.e., door to door model (DDDM), hand-out and wildlife immunization model (WIM). The DDDM was performed in the rural area of Tiflet on 60 owned dogs. The hand-out strategy was tested on 15 stray dogs. The WIM was performed on 4 transects lines near Tiflet slaughterhouse and near the weekly traditional market location. RESULTS: Using the DDDM, 100% of owned dogs were attracted by the baits and 77% ate the bait. Using the hand-out model, 100% of dogs showed interest in baits and 46.7% took the baits. Using the WIM in stray dogs, up to 73% of baits disappeared and 68% of the capsules containing the SAG2 vaccine were found pierced, depending on the sites of distribution. CONCLUSION: This pilot study showed that baits have a good palatability and that oral vaccination of both owned and stray dogs is feasible with baits specifically developed for dogs and with adapted strategy of distribution.