Prevalence and pathological investigation of fowl typhoid in commercial poultry farms at the Rajshahi City Corporation area of Bangladesh

The present study was conducted to determine the prevalence of Fowl typhoid in apparently healthy, sick and dead birds at Rajshahi city corporation area of Bangladesh. A total of 500 birds (50 from each farm) and 30 different organs (liver from 10, ovary from 8, heart from 7, and caecal tonsils from 5) were randomly collected from different commercial poultry farms during the period from January 2018 to December 2018. The prevalence study was performed based on history, clinical signs, symptoms exhibited by the individual bird of a flock during the observation of farms, and illness of birds. The suspected birds were subjected to necropsy examination. During sample collection, clinical signs and gross necropsy changes were recorded very carefully. The collected tissues were fixed, processed, sectioned, stained, and studied light microscopically. The routine histopathological method was used for the detection of tissue-level alterations in Fowl typhoid infected cases. The prevalence of Fowl typhoid in apparently healthy birds of different poultry farms was 8.2%, and 23.33% of organs were involved. Grossly, the liver was enlarged, congested and revealed bronze discoloration with focal necrosis in the surface of the liver. Old raised hemorrhages were found in the caecal tonsils. Congested, deformed, and pedunculated ova were other important findings. Microscopically, the sections of the liver showing multifocal necrosis with infiltration of heterophils and reticulo-endothelial cells. Res. Agric., Livest. Fish.8(2): 201-209, August 2021

Optimized Detoxification of a Live Attenuated Vaccine Strain (SG9R) to Improve Vaccine Strategy against Fowl Typhoid

The live attenuated vaccine strain, SG9R, has been used against fowl typhoid worldwide, but it can revert to the pathogenic smooth strain owing to single nucleotide changes such as nonsense mutations in the rfaJ gene. As SG9R possesses an intact Salmonella plasmid with virulence genes, it exhibits dormant pathogenicity and can cause fowl typhoid in young chicks and stressed or immunocompromised brown egg-laying hens. To tackle these issues, we knocked out the rfaJ gene of SG9R (named Safe-9R) to eliminate the reversion risk and generated detoxified strains of Safe-9R by knocking out lpxL, lpxM, pagP, and phoP/phoQ genes to attenuate the virulence. Among the knockout strains, live ΔlpxL- (Dtx-9RL) and ΔlpxM-9R (Dtx-9RM) strains induced remarkably less expression of inflammatory cytokines in chicken macrophage cells, and oil emulsion (OE) Dtx-9RL did not cause body weight loss in chicks. Live Dtx-9RM exhibited efficacy against field strain challenge in one week without any bacterial re-isolation, while the un-detoxified strains showed the development of severe liver lesions and re-isolation of challenged strains. Thus, SG9R was optimally detoxified by knockout of lpxL and lpxM, and Dtx-9RL and Dtx-9RM might be applicable as OE and live vaccines, respectively, to prevent fowl typhoid irrespective of the age of chickens.

Retrospective study on livestock vaccine coverage and trends in Digelu-tijo district, Arsi zone

Ethiopia has huge numbers of livestock hampered with high prevalence of infectious disease due to poor disease prevention and control. A five-year retrospective study was conducted to collect data on commonly diagnosed bacterial and viral disease and associated vaccine available at district government veterinary clinic in 2019. The commonly encountered bacterial and viral cattle diseases recorded in the case record book were LSD, CBPP Black leg, Anthrax, Bovine pasteurellosis, and Mastitis. Sheep and goat pox disease, Ovine Pasteurellosis, PPR, CCPP, and anthrax were the common diseases of sheep and goat in the study district. Regarding diseases of poultry, New castle, Infectious Bursal Diseases (Gumboro), Infectious coriza, chicken pox, Coccidiosis, Fowl Typhoid, Fowl Cholera, and Marex are the major once. The commonly available vaccines in the study district were LSD, Black leg, Anthrax, Bovine pasteurellosis, Ovine pasteurellosis, Sheep and Goat Pox, PPR, and vaccine for chicken disease like New castle disease vaccine, Gumboro, Fowl Pox, Fowl typhoid and Fowl cholera were used. Vaccination coverage for Lumpy Skin Disease, Sheep and Goat pox and Newcastle viral diseases were good compared with other diseases. The majority 36% of the population of cattle were vaccinated for LSD in 2019 and the lowest 16% in 2015.The lower portion of shoat 8% and half of the population 50% were vaccinated in 2017 and 2019 respectively. Maximum proportion of Newcastle and Gumboro vaccination coverage were 53% and 42%. The vaccination trends for most of the vaccines were fluctuating from year to year whereas the vaccination trend for LSD was increasing from year to year.

Immunogenicity and protective efficacy of irradiated Salmonella Gallinarum against homologous challenge infection in Bovans brown chickens

Fowl typhoid is a systemic poultry disease caused by Salmonella Gallinarum (SG). It is responsible for significant economic loss, due to its severe morbidity and mortality. An irradiated vaccine is one of the possible alternatives to prevent and control fowl typhoid. This study aimed to evaluate the safety, immunogenicity, and protective efficacy of irradiated SG using a randomized control trial in chicken. A field strain of SG was exposed to different doses of gamma irradiation to determine its effect on the viability of SG. Safety and immunogenicity were assessed by administering irradiated SG orally to 3 groups (5 each) of 5 weeks old Bovans brown chickens at 2400, 2500, and 2600 gray (Gy). The protective efficacy of 108colony forming units (CFU) of SG irradiated at 2400 Gy administered orally and subcutaneously was then evaluated using homologous challenge infection and compared with SG 9R commercial vaccine using 40, 5-week old Bovans brown chickens where the chickens were randomly assigned to 4 groups. Chickens in Group 1were exposed to 108 CFU of irradiated SG orally; Group 2 to the same dose subcutaneously; Group 3 to SG 9R strain commercial vaccine subcutaneously, Group 4 to phosphate-buffered saline (PBS) orally. Data related to survival, antibody response, and pathological lesions were recorded. Mann-Whitney U-test, Kruskal-Wallis test, and Fisher’s exact tests were used to examine for statistical significance. Irradiation at 2600 Gy caused complete inactivation of SG whereas SG exposed to 2400 Gy showed better immunogenicity and was safe for chickens. Antibody response in a group of chickens vaccinated with irradiated SG administered subcutaneously (SC) was significantly higher than those vaccinated with the SG 9R vaccine on day 7 (p=0.003) and day 14 (p=0.002) post-immunization. Comparative evaluation of the protective efficacy based on the mortality rate of chickens after challenge showed that 2400 Gy irradiated SG vaccine administered SC and SG 9R vaccine-induced equal protection of 50% while the irradiated vaccine administered orally protected only 10% of chickens against homologous challenge infection. SG was not isolated from the liver, spleen, and feces of chickens that survived challenge infection until the end of the experiment. Irradiated SG administered SC is shown to be a promising vaccine against fowl typhoid. Further studies using a large sample size involving tuning of irradiation dose to improve immunogenicity and use of booster vaccination are recommended. Keywords: Chicken; Fowl typhoid; Gamma irradiation; Salmonella Gallinarum; Vaccine

Evidence of vector borne transmission of Salmonella enterica enterica serovar Gallinarum and fowl typhoid disease mediated by the poultry red mite, Dermanyssus gallinae (De Geer, 1778)

Background: The poultry red mite Dermanyssus gallinae (De Geer, 1778) is a major ectoparasite of poultry. Infestations are found in most laying hen farms in Europe, and breeder flocks have also been reported to be affected. Mite infestation has detrimental effects on animal welfare, it causes significant economic losses, and, additionally, D. gallinae is often considered as a vector for pathogens. Despite suspicion of a close relationship between the poultry red mite and Salmonella enterica enterica serovar Gallinarum biovar Gallinarum ( S. Gallinarum), the causative agent of fowl typhoid disease (FT), there has been no definitive proof of mite-mediated transmission. Therefore, an investigation was conducted to determine if D. gallinae -mediated transmission of S. Gallinarum could be demonstrated among four different hen groups. Methods: Two groups of 8 hens (A and B) were experimentally infected with S. Gallinarum in two isolators. After 7 days, when birds showed signs of FT, about 25,000 mites were introduced. After 3 days, mites were harvested and used to infest two other hen groups of 8 (C and D), in two separate isolators. The health status of hens was constantly monitored; detection and quantification of S. Gallinarum were performed by PCR and qPCR from mites and organs of dead hens. The maximum likelihood estimation of the infection rate and mite vectorial capacity were calculated. Results: Clinical disease was observed in groups infected with S. Gallinarum (A and B) and in hens of groups C and D infested with mites harvested from the isolators containing groups A and B. In all 4 groups, S. Gallinarum was detected from liver, spleen, ovary, and cecum of hens, thus confirming the diagnosis of FT. Mite analysis demonstrated the presence of the pathogen, with an estimated infection rate ranging between 13.72 and 55.21 infected per thousand mites. Vectorial capacity was estimated to be 73.79. Conclusions: Mites harvested from birds infected with S. Gallinarum were shown to carry the mite, and then to transfer S . Gallinarum to isolated groups of pathogen-free birds that subsequently showed signs of FT. Mite vectorial capacity was high, demonstrating that D. gallinae should be considered an effective vector of FT.

Evidence of vector borne transmission of Salmonella enterica enterica serovar Gallinarum and fowl typhoid disease mediated by the poultry red mite, Dermanyssus gallinae (De Geer, 1778)

Background The poultry red mite Dermanyssus gallinae (De Geer, 1778) is a major ectoparasite of poultry. Infestations are found in most laying hen farms in Europe, and breeder flocks have also been reported to be affected. Mite infestation has detrimental effects on animal welfare, it causes significant economic losses, and, additionally, D. gallinae is often considered as a vector for pathogens. Despite suspicion of a close relationship between the poultry red mite and Salmonella enterica enterica serovar Gallinarum biovar Gallinarum (serovar Gallinarum), the causative agent of fowl typhoid disease (FT), there has been no definitive proof of mite-mediated transmission. Therefore, an investigation was conducted to determine if D. gallinae-mediated transmission of serovar Gallinarum could be demonstrated among four different hen groups. Methods Two groups of 8 hens (A and B) were experimentally infected with serovar Gallinarum in two isolators. After 7 days, when birds showed signs of FT, about 25,000 mites were introduced. After 3 days, mites were harvested and used to infest two other hen groups of 8 (C and D), in two separate isolators. The health status of hens was constantly monitored; detection and quantification of serovar Gallinarum were performed by PCR and qPCR from mites and organs of dead hens. The maximum likelihood estimation of the infection rate and mite vectorial capacity were calculated. Results Clinical disease was observed in groups infected with serovar Gallinarum (A and B) and in hens of groups C and D infested with mites harvested from the isolators containing groups A and B. In all four groups, serovar Gallinarum was detected from liver, spleen, ovary, and cecum of hens, thus confirming the diagnosis of FT. Mite analysis demonstrated the presence of the pathogen, with an estimated infection rate ranging between 13.72 and 55.21 infected per thousand mites. Vectorial capacity was estimated to be 73.79. Conclusions Mites harvested from birds infected with serovar Gallinarum were shown to carry the mite, and then to transfer serovar Gallinarum to isolated groups of pathogen-free birds that subsequently showed signs of FT. Mite vectorial capacity was high, demonstrating that D. gallinae should be considered an effective vector of FT.

Evidence of vector borne transmission of Salmonella enterica subsp. enterica ser. Gallinarum and fowl typhoid mediated by the poultry red mite, Dermanyssus gallinae (De Geer, 1778)

Background: The poultry red mite Dermanyssus gallinae (De Geer 1778) is a major ectoparasite of poultry. Infestations are found in most laying hen farms in Europe, and breeder flocks have also been reported to be affected. Mite infestation has detrimental effects on animal welfare, it causes significant economic losses, and, additionally, D. gallinae is often considered as a vector for pathogens. Despite suspicion of a close relationship between the poultry red mite and Salmonella enterica subsp. enterica ser. Gallinarum biovar Gallinarum (S. Gallinarum), the causative agent of fowl typhoid (FT), there has been no definitive proof of mite-mediated transmission. Therefore, an investigation was conducted to determine if D. gallinae-mediated transmission of S. Gallinarum could be demonstrated among four different hen groups.Methods: Two groups of 8 hens (A and B) were experimentally infected with S. Gallinarum in two isolators. After seven days, when birds showed signs of FT, about 25,000 mites were introduced. After 3 days, mites were harvested and used to infest two other hen groups of 8 (C and D), in two separate isolators. The health status of hens was constantly monitored; detection and quantification of S. Gallinarum were performed by PCR and qPCR from mites and organs of dead hens. The maximum likelihood estimation of the infection rate and mite vectorial capacity were calculated.Results: Clinical disease was observed in groups infected with S. Gallinarum (A and B) and in hens of groups C and D infested with mites harvested from the isolators containing groups A and B. In all 4 groups, S. Gallinarum was detected from liver, spleen, ovary, and cecum of hens, thus confirming the diagnosis of FT. Mite analysis demonstrated the presence of the pathogen, with an estimated infection rate ranging between 13.72 and 55.21 infected per thousand mites. Vectorial capacity was estimated to be 73.79.Conclusion: Mites harvested from birds infected with S. Gallinarum were shown to carry the mite, and then to transfer S. Gallinarum to isolated groups of pathogen-free birds that subsequently showed signs of FT. Mite vectorial capacity was high, demonstrating that D. gallinae should be considered an effective vector of FT.