Characterization of viral, bacterial, and parasitic causes of disease in small-scale chicken flocks in the Mekong Delta of Vietnam

Transboundary viral diseases of pigs, poultry and ruminants in Southeast Asia: a systematic review

Livestock is a strategic part of the small-farm economy in Southeast Asia's society, providing food income, clothing, fertilizer, and draught power. However, incidences or outbreaks of transboundary animal diseases (TADs) are due to converging factors such as the natural hazards' aftermath, climate change, deforestation, urban growth, changing production conditions, and market chains. Therefore, this affects productivity and impacts farmers' livelihoods with small holdings. The literature review was carried out to understand the current situation of TADs in Southeast Asia, identifying knowledge gaps to provide actions for disease control and prevention in the region. We have attempted to summarise the scientific literature in English on the prevalence data of TADs in Southeast Asia between 2011 and March 2022. Relatively few studies evaluated the distribution of TAD, where most of the studies focused on diseases that are important for international trade, such as avian influenza (AI), African swine fever (ASF), classical swine fever (CSF), foot-and-mouth disease (FMD) and Newcastle disease (ND). Traditional production systems have received little attention in such studies as they belonged to mainly smallholders. The outbreaks of ASF and lumpy skin disease (LSD) in 2019 resulted in increased research activity between 2019-2022, while the other TADs were ignored in this period. For new emerging TADs diseases such as ASF and LSD, there is only information about the first detection without prevalence information. Therefore, further epidemiological investigations are necessary to reduce the gaps in disease surveillance reporting systems and support the prevention and reduction of further outbreaks.

Factors affecting highly pathogenic avian influenza vaccination practices at poultry farms in Tra Vinh, Vietnam

Background

The increased number of cases of highly pathogenic avian influenza (HPAI) as a zoonosis has raised concerns in terms of poultry and human health. Farmers' preventive practices are an effective way of reducing zoonosis. However, this practice may have been affected by many factors, including production behaviors, awareness, and farmers' perceptions of farmers toward zoonosis.

Aim

This study was conducted on 166 poultry farms in Tra Vinh Province with 14,894 poultry heads to determine the socioeconomic profiles and production characteristics of poultry farms and analyze the effect of these factors on HPAI vaccination practices.

Methods

Respondents were selected from lists provided by government officers. Descriptive statistics were used to describe all variables, and factors affecting HPAI vaccination practices were analyzed using binary regression analysis.

Results

The results showed that most farmers raised poultry with other livestock using the free-range method, which is a semi-intensive system. The primary objectives of poultry farming are meat sales and augmenting household consumption, with farmers primarily raising chicks produced on their farms. The implementation of the vaccine was less than 50% on the surveyed farms, with a small number of farmers administering an HPAI booster dose. However, only 6% of the farmers confirmed that their livestock had been exposed to HPAI. In addition, HPAI vaccination and booster dose practices significantly increased when farmers had 4-6 family members and received HPAI prevention training. Moreover, increased poultry numbers have led to increased vaccination rates and the implementation of booster doses for poultry. The study also reported that the vaccination rate decreased when poultry was used for household consumption.

Conclusion

Sociodemographic characteristics and production behaviors can affect the implementation of HPAI vaccination on small poultry farms.

Molecular detection of respiratory avian mycoplasmosis associated bacterial and viral concurrent infections in the poultry flocks

Respiratory tract infections are of serious concern to the poultry industry. The present study was aimed to delineate the extent of respiratory avian mycoplasmosis associated bacterial and viral concurrent infections in the poultry flocks. A total of 146 poultry flocks of Haryana and Rajasthan, India, suspected for chronic respiratory disease (CRD) were screened for avian mycoplasmas, Newcastle disease virus (NDV), infectious bronchitis virus (IBV), and avian pathogenic Escherichia coli (APEC) by conventional polymerase chain reaction (PCR) assays. A total of 49.31% (72/146) flocks were found positive for Mycoplasma infection. Of the Mycoplasma-positive flocks, 80.55% (58/72) represented pathogenic avian mycoplasmas (MG and/or MS), while 19.44% (14/72) flocks were positive for commensal avian mycoplasmas (other than MG and MS). A correlation was deduced between avian mycoplasmosis and bacterial and/or viral co-infections. The results revealed that 17.24% (10/58) flocks had only avian mycoplasmosis infection. However, in the remaining flocks, the avian mycoplasmosis was associated either with APEC infection [17.24% (10/58)], IBV infection [43.10% (25/58)], or both APEC and IBV infections [22.41% (13/58)], respectively. Further epidemiological studies on respiratory avian mycoplasmosis associated concurrent infections with other pathogens are recommended to assess circulating strains, risk factors, and economic losses.

A Multiplex PCR Method for Simultaneous Detection of Infectious Laryngotracheitis Virus and Ornithobacterium rhinotracheale

To date, many fluorescence- and gel-based multiplex polymerase chain reaction (PCR) assays have been developed for the simultaneous detection of multiple infectious agents of respiratory disease in poultry. However, PCR assays are not available for other important emerging respiratory bacteria, such as Ornithobacterium rhinotracheale (ORT). We aimed to fill this gap by establishing a new duplex PCR method for the simultaneous detection of infectious laryngotracheitis virus (ILTV) and ORT. Multiplex primer design software was used to select the compatible multiplex primer pairs. It was determined that an annealing temperature of 65 °C and an initial concentration of 2.5 pmol/µL for each primer set were the most suitable conditions for multiplex PCR. The assay was confirmed to be specific, as it only detected the target pathogens, even in the presence of six non-target agents. The limit of detection was up to 10³ copies/µL of template DNA for both ILTV and ORT. In the screening of 304 field samples, 23, 88, and 44 were positive for both ILTV and ORT, solely for ILTV, and solely ORT, respectively.

Comparative Genomics Analysis and Outer Membrane Vesicle-Mediated Horizontal Antibiotic-Resistance Gene Transfer in Avibacterium paragallinarum

Avibacterium paragallinarum is the etiological agent of infectious coryza, an acute respiratory disease of chickens that is globally distributed and causes serious economic losses for chicken production. A. paragallinarum is a Gram-negative bacterium that releases outer membrane vesicles (OMVs). In this study, a comparative genomic analysis of A. paragallinarum isolate P4chr1 and its OMVs was carried out, and the ability to transfer antibiotic resistance genes (ARGs) via the OMVs was studied. Sequencing and data analyses demonstrated that the genomic size of A. paragallinarum P4chr1 was approximately 2.77 Mb with a 25 kb tolerance island that covered six types of antibiotics and 11 ARGs. The genomic size of its OMVs was approximately 2.69 Mb, covering 97% of the genomic length and almost all the gene sequences of P4chr1. Purified and DNase-treated A. paragallinarum P4chr1 OMVs were cocultured with the antibiotic-sensitive A. paragallinarum Modesto strain on an antibiotic (chloramphenicol, erythromycin, tetracycline, or streptomycin)-containing plate, and the corresponding ARGs were detected in the colonies grown on the plates. However, using an antimicrobial susceptibility test, we found that ARGs delivered by OMVs were not persistent but only appeared transiently on the antibiotic-containing plates. Antibiotic resistance and ARGs were lost by the second bacterial passage. IMPORTANCE The functions and roles of OMVs on ARG and virulent gene transfer and dissemination have been reported in numerous Gram-negative bacteria. However, the role of OMVs in mediating antibiotic resistance in A. paragallinarum has not been reported. This study is the first report to compare the genomic characteristics of OMVs with its parent A. paragallinarum strain and to study A. paragallinarum ARG transfer via OMVs. This work has provided useful data for further studies focusing on nonplasmid ARG transfer mediated by A. paragallinarum OMVs.

Molecular epidemiological studies on avian pathogenic Escherichia coli associated with septicemia in chickens in India

Bacterial septicemia causes huge economic losses in the poultry industry and there is no systematic research available in India on the connection of various pathogens associated with septicemia. The present molecular epidemiological study was conducted to investigate the association of different bacterial and immunosuppressive viral pathogens in septicemia suspected chickens. A total of 443 chicken carcasses with septicemic conditions from 71 different flocks were included in this study. Heart blood swabs were subjected to bacterial culture for Salmonella spp., Pasteurella multocida, Escherichia coli, and Gallibacterium anatis. Of these 51 flocks tested for E. coli, 49 (96.1%) flocks were found positive. Among flocks tested for Salmonella spp., 2 flocks were found positive. All tested flocks were found negative for G. anatis and P. multocida as well as air sac swabs tested negative for Mycoplasma spp. Bacterial cultural examination revealed that majority of septicemic chickens were found to be infected with E. coli and these E. coli isolates showed the highest resistance to vancomycin (60%), followed by erythromycin (50%) and cefotaxime (38%) and maximum sensitivity to cefotaxime and clavulanic acid combinations (81.5%), followed by chloramphenicol (69.6%) and ertapenem (67.2%). Among the 5 avian pathogenic E. coli (APEC) virulence genes were detected in 36 flocks and highest frequency of iss (100%), followed by ompT or iutA (97.2%), hly (61.1%) and iroN (47.2%) genes. On polymerase chain reaction (PCR) screening, 10.5, 4.5, 52.2, 19.4, 9.0, 4.5, 20.1 and 19.4% of the flocks were positive for G. anatis, Ornithobacterium rhinotracheale, APEC, Salmonella spp., Mycoplasma gallisepticum, Mycoplasma synoviae, chicken infectious anemia virus and Marek's disease virus, respectively. To our knowledge, the present study is first on the etiology of septicemia in chicken flocks in India. The present study infers that the majority of septicemic deaths in broiler chickens less than 8 weeks have been connected with APEC and majority of E. coli isolates are multidrug resistance, suggesting the need for surveillance and intervention to curb the inadvertent use of antibiotics. Although, incidence of G. anatis association with septicemia was reported, still requires a rigorous epidemiological study to determine the actual prevalence. However, more detailed studies encompassing vast geographical area with large sample size and long duration of the studies are necessary to provide a clear picture of the interaction of different pathogens causing septicemia in chicken.

Minimum inhibitory concentrations of commercial essential oils against common chicken pathogenic bacteria and their relationship with antibiotic resistance

Aims

We investigated the antibacterial effect of seven essential oils (EOs) and one EO‐containing liquid phytogenic solution marketed for poultry and pigs (‘Product A’) on chicken pathogens, as well as the relationship between minimum inhibitory concentration (MIC) in EOs and antibiotics commonly administered to chicken flocks in the Mekong Delta (Vietnam).

Methods and Results

Micellar extracts from oregano (Origanum vulgare), cajeput (Melaleuca leucadendra), garlic (Allium sativum), black pepper (Piper nigrum), peppermint (Mentha × piperita L.), tea tree (Melaleuca alternifolia), cinnamon (Cinnamomum zeylanicum) EOs and Product A were investigated for their MIC against Avibacterium endocarditidis (N = 10), Pasteurella multocida (N = 7), Ornitobacterium rhinotracheale (ORT) (N = 10), Escherichia coli (N = 10) and Gallibacterium anatis (N = 10). Cinnamon EO had the lowest median MIC across strains (median 0.5 mg/ml [IQR, interquartile range 0.3–2.0 mg/ml]), followed by Product A (3.8 mg/ml [1.9–3.8 mg/ml]), oregano EO (30.4 mg/ml [7.6–60.8 mg/ml]) and garlic 63.1 mg/ml [3.9 to >505.0 mg/ml]. Peppermint, tea tree, cajeput and pepper EOs had all MIC ≥219 mg/ml. In addition, we determined the MIC of the 12 most commonly used antibiotics in chicken flocks in the area. After accounting for pathogen species, we found an independent, statistically significant (p < 0.05) positive correlation between MIC of 10 of 28 (35.7%) pairs of EOs. For 67/96 (69.8%) combinations of EOs and antibiotics, the MICs were correlated. Of all antibiotics, doxycycline was positively associated with the highest number of EOs (peppermint, tea tree, black pepper and cajeput, all p < 0.05). For cinnamon, the MICs were negatively correlated with the MICs of 11/12 antimicrobial tested (all except colistin).

Conclusions

Increases in MIC of antibiotics generally correlates with increased tolerance to EOs. For cinnamon EO, however, the opposite was observed.

Significance and Impact of the Study

Our results suggest increased antibacterial effects of EOs on multi‐drug resistant pathogens; cinnamon EO was particularly effective against bacterial poultry pathogens.

Small-scale commercial chicken production: A risky business for farmers in the Mekong Delta of Vietnam

Small-scale farming of meat chicken flocks using local native breeds contributes to the economy of many rural livelihoods in Vietnam and many other low- and middle-income countries (LMICs). These systems are also the target of high levels of antimicrobial use (AMU); however, little is known about the profitability and sustainability of such systems. Since small-scale farms are commercial enterprises, this knowledge is essential to develop successful strategies to curb excessive AMU. Using longitudinal data from 203 small-scale (100−2,000 heads) native chicken flocks raised in 102 randomly selected farms in Dong Thap province (Mekong Delta, Vietnam), we investigated the financial and economic parameters of such systems and the main constraints to their sustainability. Feed accounted for the largest financial cost (flock median 49.5 % [Inter-quartile range (IQR) 41.5−61.8 %]) of total costs, followed by day-old-chicks (DOCs) (median 30.3 % [IQR 23.2−38.4 %]), non-antimicrobial health-supporting products (median 7.1 % [IQR 4.7−10.5 %]), vaccines (median 3.1 % [IQR 2.2−4.8 %]), equipment (median 1.9 % [IQR 0.0−4.9 %]) and antimicrobials (median 1.9 % [IQR 0.7−3.6 %]). Excluding labor costs, farmers achieved a positive return on investment (ROI) from 120 (59.1 %) flocks, the remainder generating a loss (median ROI 124 % [IQR 36–206 %]). Higher ROI was associated with higher flock size and low mortality. There was no statistical association between use of medicated feed and flock mortality or chicken bodyweight. The median daily income per person dedicated to raising chickens was 202,100 VND, lower than alternative rural labor activities in the Mekong Delta. In a large proportion of farms (33.4 %), farmers decided to stop raising chickens after completing one cycle. Farmers who dropped off chicken production purchased more expensive feed (in 1000 VND per kg): 11.1 [10.6−11.5] vs. 10.8 [10.4−11.3] for farms that continued production (p = 0.039), and experienced higher chicken mortality (28.5 % [12.0−79.0 %] vs. 16 [7.5−33.0 %]; p = 0.004). The rapid turnover of farmers raising chickens in such systems represents a challenge to the uptake of messages on appropriate AMU and chicken health. To ensure sustainability of small-scale commercial systems, advisory services need to be available to farmers as they initiate new flocks, and support them in the early stages to help overcome their limited experience and skills. This targeted approach would support profitability whilst reducing risk of emergence of AMR and infectious disease from these systems.

Prevalence of Select Intestinal Parasites in Alabama Backyard Poultry Flocks

Simple Summary

As biosecurity is generally low in backyard chicken flocks, infections with various pathogens are common. This puts other poultry nearby, including commercial flocks, at risk. Some chicken pathogens can also infect humans and cause disease. In this study, backyard poultry flocks were tested for parasites. Eighty-four fecal samples, 82 from chickens and two from turkeys, from 64 backyard flocks throughout the state of Alabama were collected in the summers of 2017 and 2018. The most frequently observed parasites were coccidia, unicellular parasites capable of causing diarrhea. Eggs of various roundworms were observed in 20.3–26.6% of the flocks. These parasites were usually present in low numbers only. Other detected parasites were the flagellates Histomonas meleagridis and Tetratrichomonas gallinarum in 4.7% and 18.8% of flocks. Both can cause severe disease in poultry. Detected parasites that can cause disease in humans were Cryptosporidium spp. in 18.8% of the flocks and Blastocystis spp. in 87.5% of the flocks. The results will help to provide information that can be used to design outreach programs to improve the health and wellbeing of birds in backyard flocks.

Abstract

Keeping chickens as backyard pets has become increasingly popular in the United States in recent years. However, biosecurity is generally low in backyard flocks. As a consequence, they can serve as reservoirs for various pathogens that pose a risk for commercial poultry or human health. Eighty-four fecal samples, 82 from chickens and two from turkeys, from 64 backyard flocks throughout the state of Alabama were collected in the summers of 2017 and 2018. Coccidia oocysts were seen in 64.1% of flocks with oocyst counts in most samples below 10,000 oocysts per gram. Eggs of Ascaridia spp. or Heterakis gallinarum were observed in 20.3% of the flocks, and eggs of Capillaria spp. in 26.6% of the flocks. Egg counts were low, rarely exceeding 1000 eggs per gram. DNA extracted directly from fecal samples was investigated by PCR for other relevant parasites. The results showed that 4.7% of flocks were positive for Histomonas meleagridis, 18.8% of flocks for Tetratrichomonas gallinarum, 18.8% of flocks for Cryptosporidium spp. and 87.5% of flocks for Blastocystis spp. The results will help to provide information that can be used to design outreach programs to improve health and wellbeing of birds in backyard flocks.

Thwaites G, Carrique-Mas JJ. Characterizing Antimicrobial Resistance in Chicken Pathogens: A Step towards Improved Antimicrobial Stewardship in Poultry Production in Vietnam

In the Mekong Delta of Vietnam, farmers use large quantities of antimicrobials to raise small-scale chicken flocks, often including active ingredients regarded of “critical importance’” by the World Health Organization. Due to limitations in laboratory capacity, the choice of antimicrobials normally does not follow any empirical criteria of effectiveness. The aim of this study was to highlight non-critically important antimicrobials against which chicken pathogens are likely to be susceptible as a basis for treatment guidelines. Microtiter broth dilution method was performed to determine the minimal inhibitory concentration (MIC) of 12 commonly used antimicrobials for 58 isolates, including Ornithobacterium rhinotracheale (ORT) (n = 22), Gallibacterium anatis (n = 19), and Avibacterium endocarditidis (n = 17). Unfortunately, internationally accepted breakpoints for resistance in these organisms do not exist. We drew tentative epidemiological cut-offs (TECOFFs) for those antimicrobial-pathogen combinations where MIC distributions suggested the presence of a distinct non-wild-type population. Based on the observed results, doxycycline would be the drug of choice for A.endocarditidis (11.8% presumptive non-wild type) and G. anatis infections (5.3% presumptive non-wild type). A total of 13.6% ORT isolates were non-wild type with regards to oxytetracycline, making it the drug of choice against this pathogen. This study illustrates the challenges in interpreting susceptibility testing results and the need to establish internationally accepted breakpoints for veterinary pathogens.