Phylogenetic and phylodynamic analyses of subtype-B metapneumovirus from chickens in Tunisia.

Swollen Head Syndrome (SHS) is an economically important viral disease of chickens caused by avian metapneumovirus (aMPV). The virus comprises 6 different subtypes (A,B,C,D, New-1 and New-2). To date, no information was available on the presence of the virus in Tunisian poultry. The present work aims to detect the presence of (aMPV) in broiler chicken in Tunisia, then to characterise the isolates in order to determine their subtype and to estimate their geographic origin of introduction. A total of 289 samples were collected, aMPV detection was detected by real time RT-PCR and molecular characterization was warried out by Sanger sequencing on the glycoprotein (G) gene. Phylogenetic analysis was carried out using Beast 2 software. Out of the 289 samples, 21 were revealed positive to aMPV. Only 2 isolates have been confirmed by sequencing analysis ; one isolate sampled in 2015 and another in 2019. Based on the partial G gene sequence, analysis of these 2 Tunisian isolates showed that they belong to subtype B. The isolate sampled in 2015, appeared to be phylogenetically related to derived vaccine strain. However, the one sampled in 2019 appeared to be a field strain. Phylodynamic analysis provided evidence that this field strain derived from a Spanish strain and probably the virus has been introduced from Spain to North Africa back in 2016. This study is the first that highlighted the circulation of (aMPV) in Tunisia. It is possible that aMPV has been circulating in Tunisia and neighboring countries without being detected. Also, multiple strains could be present and therefore multiple introductions have happened. Through this study, we shed the light on the importance of reinforcing farms biosecurity as well as virological surveillance.

Effects of humic acid and organic acids supplements on performance, meat quality, leukocyte count, and histopathological changes in spleen and liver of broiler chickens.

The aim of the present study is to evaluate the effect of Humic Acid (HA), Organic Acids (OA), and their combination (HAOA) on the growth performance, meat quality, leukocyte count, and histopathological changes in the liver and spleen of broiler chickens. A total of 2100 one-day-old mix-sexed broiler chickens were randomly divided into 4 groups with 5 replicates per treatment using 105 birds per pen (pen is used as an experimental unit). Treatments were: 1) Control (basal diet without additives), 2) Basal diet +0.1% HA, 3) Basel diet +0.1% HA+ 0.02% OA, 4) Basel diet +0.02% OA. Growth performance was not significantly affected by all dietary treatments during the experiment period. Sensory evaluation of breast meat indicated a significant positive response for color and smell corresponding to treatment 2) Basal diet +0.1% HA and treatment 3) Basel diet +0.1% HA+ 0.02% OA (P < 0.05). Birds receiving HA and HAOA developed fewer hepatic lesions compared to the control group (P < 0.05) and showed normal spleen structure with the extension of the white pulp area. Supplementation of HAOA corresponds to a lower heterophil to lymphocyte (H/L) ratio. The combination of HA and OA improves sensory attributes of cooked breast meat, H/L ratio, and preserves the histological structure of the spleen and liver of broiler chickens. HAOA can be recommended as a combined feed additive to improve broiler chickens' health.

Occurrence of Chicken Infectious Anemia Virus in Industrial and Backyard Tunisian Broilers: Preliminary Results.

Chicken infectious anemia virus (CIAV) is an economically important and widely distributed immunosuppressive agent in chickens. This study performed an epidemiological investigation on CIAV circulation in 195 Tunisian broilers, belonging to 13 lots from five industrial farms and in one rural farm. Fifteen animals were detected positive by a VP1 nested PCR. The amplicons were molecularly characterised by complete genome sequencing. All positive samples obtained in this study were from the rural farm, whereas the industrial farms sampled were negative. Nucleotide and amino acid sequence analyses showed a high degree of similarity among the sequences obtained, suggesting the circulation of a single CIAV strain in the positive lot. Phylogenetic analysis based on the CIAV VP1 nucleotide sequence and/or the complete genome showed that the sequences obtained in this study clustered with CIAV strains previously detected in Tunisia, Italy and Egypt, belonging to genogroup II. Our results highlight the need for constant CIAV surveillance in backyard chicken production.

Newly detected mutations in the Meq oncogene and molecular pathotyping of very virulent Marek's disease herpesvirus in Tunisia.

Marek's disease (MD) is a contagious avian viral disease that is responsible for large economic losses to farmers. The disease is caused by Marek's disease virus (species Gallid alphaherpesvirus 2), which causes neurological lesions, immune suppression, and tumor proliferation of lymphoid cells that invade a large number of organs and tissues. Despite widespread vaccination, Marek's disease virus (MDV), has shown a continuous increase in its virulence and has acquired the ability to overcome immune responses induced by vaccines. In the present study, the oncogenic serotype MDV-1 was detected by real-time PCR in DNA samples extracted from organs developing tumor infiltrations. Identification of the pathotype based on a 132-bp tandem repeat and sequencing and phylogenetic analysis of the Meq gene and its encoded protein allowed classification of the isolated viruses as "very virulent", with two new and unique mutations in the Meq gene resulting in amino acid substitutions. Sequencing of pp38, vIl-8, UL1 and UL44 genes did not reveal any new mutations that were characteristic of the Tunisian isolates or correlated with virulence. These results raised concerns about the ability of HVT and CVI988 vaccines, which are currently used in Tunisia and other countries, to protect chickens against highly virulent virus strains.

Virus-induced immunosuppression in turkeys (Meleagris gallopavo): A review.

Immunosuppression is characterized by a dysfunction of humoral and/or cellular immune response leading to increase of susceptibility to secondary infections, increase of mortality and morbidity, poor productivity, and welfare and vaccination failures. Humoral immune response depression is due to perturbation of soluble factors, as complement and chemokines in innate immunity and antibodies or cytokines in adaptive immunity. At the cellular immune response, immunosuppression is the consequence of the dysfunction of T-cells, B-cells, heterophils, monocytes, macrophages, and natural Killer cells. Immunosuppression in turkeys can be caused by numerous, non-infectious, and infectious agents, having variable pathological and molecular mechanisms. Interactions between them are very complex. This paper reviews the common viruses inducing clinical and sub-clinical immunosuppression in turkeys, and enteric and neoplastic viruses in particular, as well as the interactions among them. The evaluation of immunosuppression is currently based on classical approach; however, new technique such as the microarray technology is being developed to investigate immunological mediator's genes detection. Controlling of immunosuppression include, in general, biosecurity practices, maintaining appropriate breeding conditions and vaccination of breeders and their progeny. Nevertheless, few vaccines are available against immunosuppressive viruses in turkey's industry. The development of new control strategies is reviewed.

Prevalence of Coccidiosis in Free-Range Chicken in Sidi Thabet, Tunisia.

Background. Enteric diseases are an important concern to the poultry industry and coccidiosis is imposing a significant economic burden worldwide. Objectives. The main goal of the present study was to investigate the prevalence of coccidiosis in free-range chicken in Sidi Thabet, northeast Tunisia. Methods. Six hundred and thirty free-range chickens along with fecal samples were collected from 15 flocks in this region and two hundred chickens were found positive for oocysts of Eimeria spp. Intestines were dissected and examined for macroscopic lesions. The mucosa of small intestine and the caeca were examined for the presence and identification of parasitic forms using parasitology methods. The mean lesion scores were usually low (<2+) in different intestinal portions of different types of chicken and high scores (>2+) were attributed mainly to the caeca. Results. The overall rate of coccidiosis was 31.8%: E. tenella (61.5%), E. maxima (12%), and E. acervulina (1.5%). Mixed Eimeria species infection was observed with overall prevalence 26.5%. There was a statistically significant difference (P < 0.05) among infection rates, age groups, season, diarrhea, and type of chicken. Conclusion. This is the first report of coccidiosis rate in free-range chicken in this region. Further additional studies are needed to develop better preventive measures against coccidiosis in the country.