The objective of this study was to evaluate the circulation of Chicken Anemia Virus (CAV), Infectious Bursal Disease Virus (IBDV), Avian Reovirus (ARV) and Avian Encephalomyelitis virus (AEV) in properties of backyard chickens and carry out an epidemiological analysis. We evaluated 200 samples of chickens from 19 backyard chicken property. Only one property (P10) did not present serological titers for the diseases evaluated. This property is close to industrial farms as well as the other properties, however, P10 remained a few years without the breeding of chicks and these were the first poultry to be housed on site. This reinforces the importance of the fallow period for poultry production. The prevalence of virus-seroreactive birds was 78% (156/200), 64.5% (129/200), 78% (156/200), 78% (156/200) for CAV, IBDV, ARV and, EA, respectively. All the free-range farms studied are within a radius of 500 meters to 6 Km away from some establishments of industrial poultry. There was a correlation between serological titers for CAV and the frequency of disease in poultry (r = 0.6178). In places where birds are frequently sick, 30.76% reported that the disease occurs in chicks, 30.76% in broilers, 23.07% in broiler chickens and 7.69% in birds of all ages. Birds get sick more often in the summer period. The owners reported that the most common signs of disease were respiratory signs (snoring and nasal discharge) (46.15%), diarrhea (30.76%), and paralysis of wings and/or paws (38.46%). There was a correlation between the presence of untreated water in the property and serological titers for ARV (r = 0.5576). This report draws attention not only to high serological prevalence for the viruses studied but also important epidemiological aspects of backyard chicken diseases that may indirectly influence the industrial production.
Brazil is recognized worldwide for its excellence in industrial poultry farming, highlighting its technology in management, standardization in production respecting animal welfare, traceability and biosecurity. These characteristics are associated with industrial production although the practice of poor creation technology is a reality relevant to the country.
The creation of backyard chickens has been widely exploited over the years by small producers. Many of these breeding farms do not have specialized consulting to obtain adequate management yet; and due to the lack of information on basic biosecurity, they have low sanitary status and may result in the emergence of diseases. Properties with low sanitary status represent a risk for industrial poultry farming, mainly where there is intense exploitation of poultry such as in the south and southeast regions of the Brazil.
Immunosuppressive diseases are of great importance in poultry production. These make them susceptible to various other illnesses, which include zoonotic diseases, especially those transmitted by food such as salmonellosis and campylobacteriosis. Some of these diseases are difficult to control, at the same time they can cause economic losses, due to the drop in production, and a high rate of morbidity and mortality [
Caused by a DNA virus, from the Circoviridae family, CIA is evidenced by transient anemia, growth retardation, thymus hypoplasia, and other signs [
Since the mentioned diseases are extremely relevant to poultry production, monitoring and control must be continuous. Also, despite the importance of the viruses that cause these diseases in industrial poultry, little is known about their interference in backyard chicken production. Thus, the objective of this study was to evaluate the prevalence of the CAV, IBDV, ARV and AEV in properties of backyard chickens and carry out an epidemiological analysis between the serological titles, clinical disease and some biosecurity factors.
Blood samples from 200 backyard chickens aged between 12 and 56 weeks were collected in 19 free-range farms in the city of Uberlândia-MG, from March to October 2018. All free-range farms have a deficient veterinary technical assistance. Although the techniques used in this work are the routine of poultry production, the research was submitted to the CEUA (Ethics Committee on the Use of Animals) of the Federal University of Uberlândia under the number of 036/18.
From the free-range farms visited, only four were previously vaccinated, following: P5: Fowlpox Virus (FV), Infectious Bronchitis Virus (IBV), New Castle Disease (NCD) and IBDV; P9: FV, NCD; P17: NCD, FV, Marek’s Disease (MD), Infeccious Coryza (IC), IBV, IBDV; P19: FV, NCD; MD, IC and IBV.
Blood samples were obtained by puncture of the blood through the ulnar vein, with sterile and disposable needles and syringes, and stored in tubes for vacuum collection with clot activator, properly identified. These samples were stored in isothermal boxes until arrival at the laboratory of Molecular Epidemiology of the Faculty of Veterinary Medicine (FAMEV) of Uberlândia Federal University (UFU), where all blood serums were pipetting and individual tips and then forwarded to the Animal Health Laboratory for serological analysis. The method for identifying infected chicken was used a commercial ELISA indirect developed by IDEXX laboratories as indicated by the manufacturer. The antigen was placed in plaque for sensitization. After sensitization, the plates were washed and serum was then added and incubated at 18˚C - 26˚C for 30 minutes. Serum was then washed and placed along with an enzyme substrate for incubation followed by washing and adding the enzyme substrate for incubation for 15 minutes at 18˚C - 26˚C. The reaction was then interrupted by adding the Interruption Solution. The test was read based on the results obtained in the spectrophotometer by optical density and absorbance values. The calculations of the titles were automatically provided software (IDEXX). Serum samples with titrations greater than 396 should be considered positive and indicate vaccination or other exposure to IBDV, ARV and AEV. For CAV this value is 1000.
The free-range farms were evaluated as some points related to biosecurity and to the clinical signs of diseases. These were mapped relating proximity to the industrial farms of the region using Google Maps. For statistical analysis, the Kolmogorov-Smirnov test was used to verify whether the data were parametric for further analysis of the differences between averages by ANOVA. The correlation test performed was Pearson’s test. A significance level of 0.05 was considered and the Graph Pad Prism 7.0 program was used.
Serologic titers evaluated
From the free range farms visited, there was previous vaccination in the properties P5 and P19 for IBDV. The farmers were not able to inform whether the same birds evaluated in this study had been vaccinated for the mentioned diseases. However, in these country farms there was a vaccination approximately 6 and 12 months before to the collection. The mean serologic titers of the evaluated country farms for the diseases that affect the immune system and AE are described in
According the manufacturer’s guidance of the ELISA, title values above 397 are considered seropositive for IBDV, AEV and ARV and above 1000 are considered seropositive for CAV. Thus, when assessing the population mean, it is possible to notice that the properties P5, P10 and P14 were those that did not react to ARV; P8, P10, P15, P16, P18 did not react to IBDV; P10 did not react to AEV and CAV. The country farms P3, P14 and P15 were the most reacted to CAV; P8 and P12 for ARV; P14 and P19 for IBDV and P6 and P8 for AEV. The P10 was the only one that was not reagent for any of the viruses evaluated.
In addition to the evaluation of the mean serological titers, the histograms were constructed to better evaluate the serological titers in the free-range farms. For this, the titles were divided into categories exactly as recommended by the manufacturer. A histogram of serologic titer for CAV, IBDV, ARV, and EAV can be visualized in Figures 2(a)-(d) respectively.
The guidance of the ELISA recommends that the titration values from 1 are considered positive for all the evaluated agents. Thus, a high number of reagent birds can be observed for the virus investigated. The number of birds that did not react was 22% (44/200), 35.5% (71/200), 21% (42/200), and 21% (42/200) birds for CAV, IBDV, ARV, and AEV respectively. Thus, the prevalence of reagent birds for the virus was 78% (156/200), 64.5% (129/200), 79% (158/200), 79% (158/200) for CAV, IBDV, ARV, and AEV, respectively. From the country farms analyzed in 94.73% (18/19), at least one (1) bird was positive for CAV, 94.73% (1/19) for EA, 73.68% (14/19) for IBDV and 84.21% (16/19) for ARV.
The mapping of the studied free-range farms showed the large concentration of industrial farms around. All the free-range farms studied are within a radius of 500 meters to 6Km away from some establishments of industrial poultry activities (
The farm P10 was better evaluated for the understanding of the lowest serological titles. The birds of this farm are considered improved chicken bought from a company specializing in the production of backyard chicken. This farm is close to industrial farms as well as other. The P10 is 3.5 Km from a laying farm, 5.5 Km from a broiler farm, and 5.8 Km from a breeding broiler farm in addition to the proximity to other backyard farms (1.5 to 1.8 Km from P2 and P12) (
Disease evaluates and serological titers
A total of 68.42% (13/19) farms answered that poultry often get sick and there was a correlation between serological titers for CAV and the frequency of disease in poultry (r = 0.6178). In places where birds are frequently sick, a total of 30.76% (4/13) reported that the disease occurs in older animals, 30.76% in broilers (4/13), 23.07% in chicks and 7.69% in animals of all ages. When the farmers were asked about the time of year that most of the birds get sick 69.23% (9/13) answered that the diseases occur in the summertime, 15.38% (2/13) in the wintertime and 15.38% (2/13) in both periods. The owners reported that birds became sick with respiratory signs (snoring and nasal discharge) (46.15% (6/13)), diarrhea (30.76% (4/13)) and paralysis of wings and/or paws (38.46% (5/13)), with signs can be observed at the same time or not. It is important to report that during our visits, the main clinical symptoms observed were those related to the respiratory tract (mucus in the nostrils, swollen head and tearing). There was a correlation between the presence of untreated water in the property and serological titers for ARV (r = 0.5576).
There was no correlation between serological titles and characteristics of the farm, multispecies breeding, and cleaning of facilities. In free-range farms where there were multispecies breeding the most common birds were hens, ducks, and geese.
In Brazil, the epidemiological status of backyard chickens is poorly studied and the prevalence of antibodies to IBDV, CAV, AEV, and ARV is not well known. In the present study, IBDV presented a prevalence of 64.5% and 78% for CAV,
CAV | IBDV | ARV | AEV | |
---|---|---|---|---|
How often birds get sick (p; r) | 0.0048; 0.6178 | 0.3637; −0.2208 | 0.088; 0.401 | 0.4398; 01884 |
Characteristic of the farm (p; r) | 0.5863 −0.1333 | 0.2764 −0.2631 | 0.9378 −00.192 | 0.8376 −0.05042 |
Multispecies (p; r) | 0.2682 −0.2675 | 0.2964 −0.2528 | 0.3084 0.2468 | 0.6268 0.1192 |
Cleaning and Desinfection** (p; r) | 0.6324 −0.1706 | 0.7908 0.06522 | 0.1731 −0.326 | 0.4851 0.0652 |
Untreated water (p; r) | 0.4568 −0.184 | 0.2681 −0.2676 | 0.0131 0.5576 | 0.5530 0.1452 |
*Poultry often got sick—answered by the owner and/or observed during the visit. Characteristic of the farm: extensive or semi intensive. **All facilities were rated as reasonable or poor cleaning condition.
AEV or ARV. Titles values for IBDV were also high in backyard chicken in Rio Grande do Sul (80.2%) [
Although some researches mention the high prevalence of virus evaluated in backyard chickens, it is not common to find reports of clinical disease in these poultry. As discussed by Barrios et al. [
The fact that most of the analyzed free-range farms had at least one positive bird for the agents studied (CAV (94.73%), AEV (94.73%), ARV (84.21%) and IBDV (73.68%) illustrates the permanence or periodic circulation of these pathogens in these backyard productions. The high frequency of farms with seroconvertion of poultry indicates a risk of introduction of agents that are distributed in nature in poultry commercial farms. However, it should also be considered that the region where the backyard production is located in this study is a site of the rich production of breeding broiler that is widely immunized with live vaccines for IBDV, AEV and CAV. In this way, the possibility of transmission of the vaccine strains from industrial birds to backyard chicken should be considered.
Several reports reinforce that the presence of immunosuppressive agents favors the establishment of pathogenic microorganisms of importance also for public health. Sheela et al. (2003) observed that birds infected with CAV had depressed immune responses, especially the mucosal immune responses in co-infection with Salmonella Enteritidis. According to McNamee et al. [
When evaluating the serological prevalence of the free-range farms (ARV, IBDV, AEV, and CAV) only the P5 and P17, reported the vaccination for IBDV, and the P9 and P19 presented reports of vaccination, but for other diseases. The results of IBDV titers for the vaccinated birds are within the positivity line for the disease. Antibody titers of a virus challenge in the field tend to be higher than vaccines titers. For this, it is necessary to establish a timeline for the evaluation of the levels of antibodies of the evaluated diseases, during different stages of the life of the birds. Property P17 presented higher average titers than the P5 property, but without evaluation of the historical titles it is not possible to affirm that vaccination or challenge-to-field titles. What can be verified, however, is that the vaccinated properties presented titers similar or even lower than other properties without reports of vaccination, for example P2, P7, P9, P12, P14, P19.
It was verified the high density of industrial breeder broilers in the proximities with the country farms of this study (
Studies show that ARV, CAV, AEV and IBDV are resistant to environmental conditions and disinfection [
Lack of vaccination, stress due to coexistence with other birds, and dirty environment are predisposing factors to viral, bacterial or fungal infectious diseases [
Although the importance of multispecies creation for the increase of diseases is recognized, in this study, the presence of poultry of different species on the same property has not interfered with serological titers. For most of the diseases evaluated in this work, the natural host is the chicken, and perhaps, for this reason, the correlation between multispecies creation and the high serological title was not found. However, the presence of multispecies of birds in the same property can be considered an alert because of the possibility of mutation and genetic recombination of the agents facilitated by the interspecies dissemination.
In the correlation study, CAV showed a correlation with the parameter “poultry get sick frequently” with r = 0.6178. According Mukaka [
The CIA is a disease of young birds, characterized by marked anemia, bone marrow hypotrophy, increased mortality, reduced weight gain, and generalized atrophy of lymphoid organs [
The summertime was reported as the most critical for disease manifestation. In the region where poultry is raised, summer is a period associated with rain, where high temperature and humidity can favor the spread of numerous pathogens.
The presence of ARV titers in the present study showed a correlation with untreated water, probably explained to be a virus resistant to environmental conditions and disinfection [
This report draws attention not only to high serological prevalence for the viruses studied but also to epidemiological aspects important for diseases in backyard chicken who may indirectly influence birds in industrial production. The report reinforces that even in countryside areas the period of downtime decreases the infection pressure and also shows that the presence of CAV in the properties may predispose to other clinical diseases in birds. Surveillance for the virus assessed in this study should be constant in backyard chicken production since the proximity to industrial poultry production may lead to cross-contamination which may result in the appearance of strains with genetic alterations in the future.
The authors declare no conflicts of interest regarding the publication of this paper.
Almeida, P.C., Borges, P.R.S., Koerich, P.K., Melo, R.T., Batista, I.A., Mendonça, E.P., Silva, R.R., Silva, L.K. and Fonseca, B.B. (2020) Circulation of Immunosuppressive Viruses and Avian Encephalomyelitis Virus in Backyard Chicken Flocks. Advances in Microbiology, 10, 203-213. https://doi.org/10.4236/aim.2020.105016