Introduction
Poultry farming is a type of livestock husbandry in which domesticated avian species such as chickens, turkeys, ducks, and geese are raised to produce meat or eggs for food [1,2]. Farmers also raise some other avian species like guinea fowls and quails. By-products such as feathers and poultry manure are also of significant commercial value. The poultry industry has been known for decades to contribute to the economic growth of countries worldwide. For instance, in the United States of America, the poultry industry is said to provide over 2 million jobs, $125.6 billion in wages, $555.9 billion in economic activity, and $33.7 billion in government revenue [3]. In South Africa, the poultry industry is the largest single contributor to the agricultural sector. About 16.6% of total agricultural gross value and 39.9% of animal product gross in 2021 came from poultry production [4].
The Nigerian poultry industry is also not left out. It contributed about 25% to the agricultural GDP [5]. Nigeria has Africa’s largest egg production and second-largest chicken population [6]. In 2015 the poultry population in Nigeria was reported to be about 165 million [7]. In 2018, the population was 180 million birds with annual production of 1.5 million tons of poultry meat, 200 million day-old chicks, and egg production of about 16 billion with an annual turnover of over $ 3.2 billion [8]. It is important to say that the industry attaining such potential has not been without challenges. Some of the factors that impede the growth of the Nigerian poultry industry are: the high cost of feed, hoarding of major feed raw materials such as maize by middle men, high cost of day old chicks, the high interest rate on loans from banks, egg glut/egg price manipulation by middle men, importation of frozen chicken, substandard drugs and vaccines, wrong government policies and disease outbreaks [9].
Diseases that affect poultry may be infectious or non-infectious. Their effect can lead to colossal losses to farmers [10,11]. Viruses, bacteria, parasites, and fungi could cause infectious diseases that affect poultry. Of these, bacterial diseases seem to be the most occurring [12]. They could be vertically transmitted from parent stock to their progeny (chicks, poults, and so on), horizontally transmitted among sick birds, or through ingesting contaminated feed and water [13]. Examples of common bacterial diseases of avian species are colibacillosis, salmonellosis, fowl cholera, pseudomoniasis, infectious coryza, staphylococcosis, and so on. This is even worsened by the abuse or misuse of antibiotics by stakeholders in the poultry value chain. While the world is targeting the need to ensure food security, the current problem that may be faced from poultry products like meat and eggs would be food safety. This is in view of the fact that some poultry farmers who abuse antibiotics (in a bid to control undiagnosed diseases) are contributing to the problem of antimicrobial resistance (AMR) and drug (antibiotic) residues in poultry meat and eggs. This has a negative implication on the health of humans who ignorantly consume such. The importance of bacterial disease and AMR to the poultry industry necessitated the conduct of this study. Hence, this article is a report of avian cases of bacterial disease outbreaks and antibiotic resistance profiles of bacteria isolated within three years (2020–2022) at the Poultry and Fish Clinic of the Veterinary Teaching Hospital, University of Jos, Nigeria.
Materials and methods
The study location
The study setting is in Jos North local government area of Plateau state, one of Nigeria’s north-central states. The Poultry and Fish Clinic of the Veterinary Teaching Hospital (VTH) of the University of Jos is located in Jos North (9°56’ 21.73”N 8° 54’ 7.96” E), specifically close to the Polo field roundabout at the central part of the town. In this Clinic, various samples like moribund birds, fresh carcasses of birds, labeled swabs of oculo-nasal discharges, feed, and water samples were presented for microbial analysis from farms within Plateau state and other neighboring locations such as Nasarrawa, Abuja, Bauchi, and Kaduna states.
Methodology
A retrospective review and analysis of records of cases received at the Poultry and Fish Clinic of the VTH between January 2020 and December 2022 was done. The data obtained from the records are as follows: Bird type(chicks, pullets, layer, broiler, turkey, and so on), number of cases per month, number of antibiotic susceptibility tests conducted per month, pattern of antibiogram (susceptible, intermediate, and resistant) and isolate identity. The information on the type of management system (deep litter or battery cage) and type/brand of feeds that birds consumed were obtained during the clerking of each of the cases when farmers visited the clinic.
Microbial analysis and antibiotic susceptibility testing
Organs (liver, spleen, kidney, lung, and heart) harvested during post-mortem examination of carcasses were subjected to microbial analysis. Organ surfaces were seared, and inocula were taken by inserting sterile swabs and streaking them on MacConkey agar and Blood agar (containing 5% sheep blood). Presumptive bacterial cultures were identified using colony morphology, Gram-staining for cellular morphology, and biochemical characterization as described [14]. Also, isolates were identified using Bergey’s manual of determinative bacteriology [15]. For the antibiotic susceptibility test, the susceptibility of the isolated bacteria was evaluated against nine panels of antibiotics including Enrofloxacin(250 μg), Streptomycin(300 μg), Penicillin-streptomycin(150IU/300 μg), Florfenicol (300 μg), Oxytetracycline (250 μg), Tylosin (250 μg), Colistin (480 IU), Furaltadone (300 μg), and Gentamicin (250 μg). These antibiotic discs were prepared within the laboratory with justification. Organ swabs were collected and seeded onto the surface of sterile Muellar Hinton Agar (MHA) using directly from specimen antimicrobial susceptibility testing method as described by Rosemary [16]. Antibiotic discs were then gently placed onto the surface of the MHA with the aid of sterile forceps and allowed to dry before the plates were incubated aerobically at 37°C for 16 hours. After that, the diameter of the zone of inhibition (DZI) was measured and interpreted. Only bacteria with DZI of 15 mm and above were considered susceptible to the antibiotic. This interpretation is based on Clinical and Laboratory Standard Institute guidelines for Escherichia coli and other enteric Gram-negative rods [17]. In situations where the DZI is between 10 mm and 14 mm, the isolate is considered intermediate to the antibiotic, and where the DZI is less than 10 mm, it is resistant.
Statistical analysis
Data were entered into Microsoft Excel 2013 and then cleaned to remove duplicates and cases that did not meet inclusion criteria. The data were analyzed to describe the classification and number of cases handled based on bird types per year, the type/brands of poultry feed used in farms, types of bacteria isolated from tissues of sick and fresh carcasses of birds, and responses from farmers on type of system used in raising chickens. Ratios of susceptible to resistant isolates for each antibiotic were also shown. All the calculated data were presented in tabular form.
Results
Demographic details, occurrence of bacteria, and antibiotic susceptibility profiles
The bird types that were presented (mostly carcasses) for examination and laboratory tests were chicks (day 1 to week 8 of age), pullets/growers (weeks 9–19 of age), commercial layers (above 19 weeks of age), turkeys, layer and broiler parent stock (p.s.), commercial broilers, cockerels and others which consisted of geese, ducks, pigeons, peacocks, parrots, and ostriches. A breakdown of the number of cases based on bird types in the years 2020, 2021, and 2022 is shown in Table 1. The total cases handled between January 2020 and December 2022 was 6,940.
Table 1.
Classification and number of cases handled based on bird types per year.
| Bird type | Year 2020 | Year 2021 | Year 2022 |
|---|---|---|---|
| Chicks | 187 (8.75%) | 337 (12.92%) | 239 (10.89%) |
| Pullets | 226 (10.6%) | 373 (14.3%) | 307 (13.99%) |
| Layers | 1,136 (53.13%) | 1,338 (51.3%) | 1,215 (55.38%) |
| Broilers | 328 (15.34%) | 304 (11.7%) | 270 (12.31%) |
| Layer (parent stock) | 4 (0.18%) | 0 (0%) | 4 (0.18%) |
| Broiler (parent stock) | 7 (0.33%) | 2 (0.07%) | 2 (0.09%) |
| Turkeys | 127 (5.94%) | 92 (3.53%) | 45 (2.05%) |
| Cockerels | 20 (0.94%) | 11 (0.42%) | 5 (0.23%) |
| Others (geese, pigeons, ostriches etc) | 103 (4.82%) | 151 (5.79%) | 107 (4.87%) |
| Total | 2,138 | 2,608 | 2,194 |
The number of bacterial isolates from tissues of birds tested in the years 2020, 2012 and 2022 were 1,506, 2,377, and 2,100, respectively, as shown in Table 2. The bacterial isolates were E. coli, Klebsiella spp, Salmonella spp, Proteus spp, Bacillus spp Pasteurella spp, Pseudomonas aeruginosa, Streptococcus spp, Staphylococcus spp, Aeromonas spp and some uncharacterized bacteria (UCB).
Table 2.
Types of bacteria and frequency of isolation from tissues of carcasses presented.
| Bacterial Isolates | Year 2020 | Year 2021 | Year 2022 |
|---|---|---|---|
| Escherichia coli | 696 (46.22%) | 1654 (69.58%) | 1204 (57.33%) |
| Klebsiella spp | 296 (19.65%) | 565 (23.77%) | 325 (15.48%) |
| Salmonella spp | 180 (11.95%) | 25 (1.05%) | 25 (1.19%) |
| Proteus spp | 235 (15.6%) | 59 (2.48%) | 352 (16.77%) |
| Bacillus spp | 4 (0.27%) | 8 (0.34%) | 15 (0.71%) |
| Pasteurella spp | 22 (1.46%) | 3 (0.13%) | 61 (2.90%) |
| Pseudomonas aeruginosa | 23 (1.53%) | 8 (0.34%) | 31 (1.48%) |
| Streptococcus spp | 27 (1.79%) | 28 (1.18%) | 33 (1.57%) |
| Staphylococcus spp | 10 (0.66%) | 16 (0.67%) | 22 (1.05%) |
| Aeromonas spp | 13 (0.86%) | 2 (0.08%) | 2 (0.09%) |
| Uncharacterized bacteria (UCB) | 0 ( 0%) | 9 (0.38%) | 30 (1.43%) |
| Total | 1,506 | 2,377 | 2,100 |
The results of the antibiotic susceptibility profiles of these bacterial isolates in each year are as shown in Tables 3 to 5. Also, the yearly ratio of susceptible bacterial isolates to resistant bacterial isolates is shown for each of the antibiotics in Table 6. In contrast, Table 7 shows four antibiotics to which most of the bacterial isolates were most resistant to and their percentages relative to the total number of bacterial isolates subjected to antibiotic susceptibility tests. Table 8 shows a breakdown of responses from farmers on the type of management system used in raising birds on their farms. It was either a deep litter system or a battery cage system. There were 6,771 responses from those using the deep litter system and 40 from those using the battery cage system between January 2020 and December 2022.
Table 3.
Antibiogram of avian bacterial isolates to Colistin, Enrofloxacin, Gentamicin with susceptibility to resistance (S:R) ratios.
| (Year 2020) | (Year 2021) | (Year 2022) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Antibiotic | Month | Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
| Colistin | January to December | 565 | 625 | 317 | 222 | 736 | 1323 | 161 | 512 | 1,429 |
| S:R RATIO | 1.78:1 | 0.167:1 | 0.113:1 | |||||||
| Enrofloxacin | January to December | 1,036 | 430 | 78 | 1,535 | 574 | 241 | 1,070 | 618 | 414 |
| S:R RATIO | 13.28:1 | 6.36:1 | 2.58:1 | |||||||
| Gentamicin | January to December | 839 | 487 | 180 | 1,625 | 458 | 264 | 1,074 | 454 | 575 |
| S:R RATIO | 4.66:1 | 6.15:1 | 1.87:1 | |||||||
Table 4.
Antibiogram of avian bacterial isolates to Streptomycin, Penstrep®, Florfenicol with susceptibility to resistance (S:R) ratios.
| (Year 2020) | (Year 2021) | (Year 2022) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Antibiotic | Month | Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
| Streptomycin | January to December | 723 | 578 | 209 | 400 | 654 | 1,295 | 724 | 772 | 603 |
| S:R RATIO | 3.46:1 | 0.308:1 | 1.20:1 | |||||||
| Penstrep® | January to December | 815 | 578 | 114 | 1,748 | 459 | 130 | 1,054 | 555 | 492 |
| S:R RATIO | 7.15:1 | 13.45:1 | 2.14:1 | |||||||
| Florfenicol | January to December | 710 | 126 | 43 | 775 | 1,094 | 507 | 721 | 787 | 594 |
| S:R RATIO | 16.5:1 | 1.53:1 | 1.21:1 | |||||||
Table 5.
Antibiogram of avian bacterial isolates to Tylosin, Furaltadone, Oxytetracycline with susceptibility to resistance (S:R) ratios.
| (Year 2020) | (Year 2021) | (Year 2022) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Antibiotic | Month | Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
Susceptible isolates (S) | Intermediate isolates (I) |
Resistant isolates (R) |
| Tylosin | January to December | 26 | 468 | 970 | 36 | 622 | 1639 | 19 | 228 | 1852 |
| S:R RATIO | 0.03:1 | 0.021 | 0.01:1 | |||||||
| Furaltadone | January to December | 522 | 557 | 397 | 383 | 739 | 1,196 | 243 | 651 | 1,208 |
| S:R RATIO | 1.31:1 | 0.32:1 | 0.20:1 | |||||||
| Oxytetracycline | January to December | 16 | 117 | 1,346 | 3 | 159 | 2,159 | 10 | 38 | 2,055 |
| S:R RATIO | 0.012:1 | 0.001:1 | 0.005:1 | |||||||
Table 6.
Ratio of susceptible to resistant avian bacterial isolates in years 2020 to 2022.
| Antibiotic | Year 2020 S:R Ratio |
Year 2021 S:R Ratio |
Year 2022 S:R Ratio |
|---|---|---|---|
| Enrofloxacin | 13.28:1 | 6.36:1 | 2.58:1 |
| Gentamicin | 4.66:1 | 6.15:1 | 1.87:1 |
| Penstrep®(Penicillin-streptomycin) | 7.15:1 | 13.45:1 | 2.14:1 |
| Streptomycin | 3.46:1 | 0.308:1 | 1.20:1 |
| Florfenicol | 16.5:1 | 1:53:1 | 1.21:1 |
| Furaltadone | 1.31:1 | 0.32:1 | 0.20:1 |
| Tylosin | 0.03:1 | 0.02:1 | 0.01:1 |
| Colistin | 1.78:1 | 0.167:1 | 0.113:1 |
| Oxytetracycline | 0.012:1 | 0.001:1 | 0.005:1 |
Table 7.
Antibiotics to which avian bacterial isolates were most resistant.
| Furaltadone | Oxytetracycline | Colistin | Tylosin | |
|---|---|---|---|---|
| Resistant isolates in 2020 | 397 | 1,346 | 317 | 970 |
| Resistant isolates in 2021 | 1,196 | 2,159 | 1,323 | 1,639 |
| Resistant isolates in 2022 | 1,208 | 2,055 | 1,429 | 1,852 |
| Total | 2,801 | 5,560 | 3,069 | 4,461 |
| Percentage relative to total isolates tested | 45.7% | 90.69% | 50.1% | 72.8% |
Table 8.
Responses from farmers on type of system used in raising chickens.
| Poultry farmers using deep litter system | Poultry farmers using battery cage | |||||
|---|---|---|---|---|---|---|
| Year 2020 | Year 2021 | Year 2022 | Year 2020 | Year 2021 | Year 2022 | |
| January | 175 | 240 | 210 | 0 | 0 | 3 |
| February | 165 | 185 | 160 | 2 | 1 | 1 |
| March | 203 | 242 | 227 | 0 | 0 | 5 |
| April | 103 | 201 | 196 | 0 | 0 | 1 |
| May | 203 | 232 | 225 | 0 | 0 | 3 |
| June | 172 | 285 | 150 | 0 | 1 | 1 |
| July | 193 | 270 | 149 | 1 | 3 | 2 |
| August | 159 | 139 | 153 | 3 | 1 | 2 |
| September | 170 | 199 | 241 | 0 | 0 | 1 |
| October | 143 | 176 | 168 | 0 | 2 | 0 |
| November | 176 | 213 | 160 | 3 | 1 | 3 |
| December | 168 | 169 | 151 | 0 | 0 | 0 |
| Total | 2,030 | 2,551 | 2,190 | 9 | 9 | 22 |
| Grand total | 6,771 (99.4%) | 40 (0.6%) | ||||
Farmers within Jos and its environs gave responses to questions on the type/brand of poultry feed used in their farms. There were 14 branded feeds and the others were unbranded (self-milled). Of the 1,684, 2,102, and 1,720 respondents in 2020, 2021, and 2022, respectively, those of them that were using self-milled feeds were 394, 602, and 530, respectively, as shown in Table 9.
Table 9.
Farmers responses on type/brand of poultry feed used in their farms.
| Feed type | Year 2020 | Year 2021 | Year 2022 |
|---|---|---|---|
| Vital® feed | 388 (23.04%) | 379 (18.03%) | 266 (15.46%) |
| Hybrid® feed | 340 (20.19%) | 364 (17.32%) | 236 (13.72%) |
| Top® feed | 98 (5.82%) | 215 (10.23%) | 226 (13.13%) |
| Chikun® feed | 133 (7.89%) | 156 (7.42%) | 147 (8.54%) |
| Livestock® feed | 65 (3.85%) | 51 (2.42%) | 55 (3.19%) |
| Sunseed® feed | 90 (5.34%) | 117 (5.56%) | 69 (4.01%) |
| Ultima® feed | 97 (5.76%) | 136 (6.47%) | 102 (5.93%) |
| Self-milled feed (unbranded) | 394 (23.39%) | 602 (28.63%) | 530 (30.81%) |
| Animal care® feed | 12 (0.71%) | 25 (1.18%) | 36 (2.09%) |
| Rico Gado® feed | 10 (0.59%) | 0 (0%) | 0 (0%) |
| Supreme® feed | 34 (2.02%) | 22 (1.04%) | 26 (1.51%) |
| Amo® feed | 14 (0.83%) | 28 (1.33%) | 11 (0.64%) |
| Breedwell® feed | 4 (0.24%) | 4 (0.19%) | 1 (0.06%) |
| Jagaban® feed | 5 (0.29%) | 2 (0.1%) | 9 (0.52%) |
| Ecwa® feed | 0 (0%) | 1 (0.05%) | 6 (0.35%) |
| Total | 1,684 | 2,102 | 1,720 |
Discussion
Among the bird types handled for necropsy and microbial analysis of diseased organs, the commercial layers were predominant across the three survey years. High levels of disease outbreaks involving laying birds may also be linked to stress associated with daily egg production. It was observed [18] in a flock that 49% of total mortalities occurred in the laying stage, 26% during brooding, and 24% in the growing phase.
It is well known that several bacterial pathogens can invade the avian reproductive system of actively laying females. One of these is the avian pathogenic Escherichia coli (APEC), a Gram-negative bacillus, a Gram-negative bacillus, and a Gram-negative bacillus member of the Enterobacteriaceae. It often causes conditions such as oophoritis and coliform salpingitis [19,20]. The high level of cases involving commercial layers may also attest that most poultry farms in Nigeria seem to be more into the production of table eggs. Pullets and commercial broilers were other bird types handled with high bacterial disease occurrence.
Various bacterial pathogens were isolated from birds’ tissues presented at the Clinic. The most frequently isolated were E. coli, Klebsiella spp, Proteus spp, and Salmonella spp (Table 2) in decreasing order. The APEC isolates were mainly from harvested diseased organs such as yolk sacs, livers, kidneys, and spleen thus reflecting the invasiveness of these isolates. Colibacillosis this APEC causes is associated with omphalitis, perihepatitis, egg peritonitis, cellulitis, salphingitis, coligranuloma, and arthritis [21]. It is often transmitted via the fecal-oral route.
APEC has been shown to also have zoonotic potential because of genetic similarities and common characteristics of its virulence genes with human uropathogenic E. coli and neonatal meningitis E. coli. This zoonotic effect can occur via foodborne contaminations [22]. Like other bacterial pathogens affecting avian species, APEC could be transmitted vertically via contaminated drinking water, feed, and environment. As shown on Table 2, the high incidence of Colibacillosis in the cases handled over the 3 years may be linked with the fact that over 98% of farmers who presented cases at the Clinic mentioned that their birds were raised on the deep litter, making fecal-oral route a possible means of pathogen transmission. In southwest Nigeria, a high incidence of APEC had also been reported [23]. In this case, 509 (54.26%) bacterial isolates from tissues of dead layers out of 938 were APEC.
The remarkable drop in the incidence of Salmonellosis from 180 cases in 2020 to 25 cases in 2021 and 2022 is likely due to some key measures we implemented by educating commercial and parent-stock poultry farmers on the right species of Salmonella to vaccinate against while ensuring strict adherence to other biosecurity measures. Some researchers [24] and [25] have shown that the prevalent species of Salmonella causing high mortalities in farms was Salmonella enterica Serovar Enteritidis after isolation, biochemical characterization, and genome sequencing. Based on these observations and knowing that this organism causes a zoonotic disease in man, our emphasis to farmers was to administer the inactivated S. Enteritidis + S. Typhimurium vaccine to birds at weeks 12 and 14 of age. This measure helped many farmers.
Our experience with microbial analysis of feed and water samples from poultry farms has shown Klebsiella spp to be prominent among isolated bacteria. These two items (feed and water) are what farmers administer to birds every day. The implication is that if both feed and water are not sanitized before giving birds to consume, the chances of feed and water-borne bacterial infection will be high. From our survey, the highest bacterial disease outbreaks after colibacillosis were those caused by Klebsiella spp.
Tables 3–5 revealed the susceptibility and resistance pattern of over 5,900 avian bacterial isolates to 9 different antibiotics over a period of 3 years.
Oxytetracycline is a commonly used antibiotic among farmers. Our survey over a period of three years showed that 90.69% (5,560) of all avian bacterial isolates tested against it were resistant to it (Table 7). High resistance to oxytetracycline has also been reported [26] and [27]. The very poor susceptibility to resistance (S:R) ratio as seen in Tables 5 and 6 further attests to this problem of AMR. In the case of oxytetracycline, the possible abuse may not be far from the observation that it is seen as a “tonic” for boosting egg production in layers as some commercial preparations often have it combined with multivitamins and is also a consistent ingredient in the “ceryl” groups of poultry drug combinations often used during brooding of day-old chicks. Without any laboratory tests, poultry farmers are usually quick to buy these drug mixtures containing oxytetracycline. Next to this is Tylosin, a commonly used macrolide in Veterinary practice. Tables 5 and 7 clearly show the increasing level of resistance of avian bacterial isolates to this antibiotic between 2020 and 2022, i.e., from 970 resistant isolates to 1,852 resistant isolates, respectively. Unfortunately, poultry farmers often see this drug as a panacea for any type of respiratory disease in birds, not minding if the cause is viral, parasitic, or fungal. Table 7 shows that about 72.8% of all avian bacterial isolates tested between 2020 and 2022 were completely resistant to Tylosin.
Two other antibiotics to which the avian bacterial isolates showed increasing resistance patterns from 2020 to 2022 were colistin and furaltadone as shown by the declining S:R ratio in Tables 3, 5, and 7. A high level of resistance to colistin is shown here from about 50% of all avian bacterial isolates tested between 2020 and 2022 (Table 7). Colistin is a drug that has been considered a last resort when handling drug-resistant infections. The persistent resistance of avian bacterial isolates to this antibiotic may be linked to its continuous use in different forms especially in drug combinations that may have a cocktail of 4–5 antibiotics in one preparation. Some people also use colistin as a feed additive [28], which has consequences for humans. Large quantities of colistin pharmaceutical raw material are being produced in China which exported about 2,664.8 tons of it between 2018 and 2021 to 21 countries [28]. Despite the ban on furaltadone in Nigeria, about 45.7% (2801) of total avian bacterial isolates tested were resistant to it. It is currently hardly seen in Veterinary pharmacy stores. Its ban has been because of its carcinogenic tendencies [29,30].
As of 2020, the S:R ratio of avian bacterial isolates tested against Enrofloxacin was high (13.28 :1). However, this declined to 6.36: 1 and 2.58:1 in 2021 and 2022, respectively. With time, we realized that many poultry farmers tend to use this drug on their own, and it is when the mortality of birds persists they visit the Clinic to learn why the drug did not work. In the last 3 years, we have also realized that there are some sub-standard Enrofloxacin brands in circulation. These can contribute to the marked increase in resistance of avian bacterial isolates to Enrofloxacin.
Though used as an antibiotic sensitivity disc for only 7 months in 2020, florfenicol had a promising start with S:R ratio 16.5: 1, which rapidly declined in 2021 and 2022 to 1.53:1 and 1.21:1, respectively. The S:R ratio of the 2 aminoglycosides against which avian bacterial isolates were tested (gentamicin and streptomycin) seemed to have undulating patterns between 2020 and 2022. Penstrep®(Penicillin +streptomycin) seemed to have a better S:R ratio when compared with streptomycin. This may be due to the synergism between the two drugs. The S:R ratio of Penstrep® peaked at 13.45: 1 in 2021 (Table 4).
Between January 2020 and December 2022, there were 6,811 respondents to the farmers’ questions on the type of management system used in their farms. Out of these, 6,771 (99.4%) responded that they were using deep litter systems while others were using battery cages, especially in the layer section of the farms. Within Plateau state (where many potatoes and vegetables are cultivated), there is a very high demand for poultry litter by crop farmers. They seem to prefer poultry manure from deep litter to battery-caged birds. The implication is that a significant portion of these highly resistant isolates are also transmitted into the soil (environment) along with residues of drugs in the poultry faeces. This has a way of returning to the man who ingests the crops. It is also important to mention that fecal-oral transmission of bacterial infections easily occurs in deep litter systems where birds have unhindered access to the litter on the floor.
It was also observed from records of history taken when farmers visited the clinic with cases that a significant portion (23%–30%) of farmers were using self-milled feeds. These self-milled poultry feeds are unbranded (Table 9) and some farmers tend to gravitate to the toll millers to produce feeds for them because of the higher costs of branded feeds. There is the likelihood that farmers recycle empty bags to collect milled feeds and where there are no proper biosecurity measures in this, infections can spread across farms from such a feedmill.
Considering the fact that some bacterial infections in birds are a fallout of intestinal dysbiosis (imbalance between beneficial and pathogenic microbiota) [31], the associated pathogens can spread via loss of intestinal integrity into the blood stream to result in systemic bacterial infection. To avoid this, poultry farmers need to ensure the early onset of the use of probiotics in chicks to ensure a good balance in gut microflora. Probiotics are non-pathogenic microbes that exert health benefits to the host when administered in adequate quantity [32]. Consistent use of probiotics via feed will ensure that beneficial bacteria like Lactobacillus acidophilus, Lactobacillus bulgaricus, Lactobacillus rhamnosus, and Bifidobacterium bifidum are able to exert competitive exclusion to ensure the pathogenic bacteria in the gut are suppressed [33,34].
The consistent use of feed-grade organic acids in feed production is one of the ways by which feed millers can help reduce the need for administering antibiotics in birds. These organic acids like propionic acid, formic acid, acetic acid, and lactic acid have an inhibitory effect on the gut pathogenic bacteria by lowering the pH in the cytoplasm of bacterial cells, thus interfering with their metabolism and growth thus favoring those of the beneficial bacteria that thrive better with reduced pH [35]. A blend of these organic acids may be used at 1.5–2 kg/ton of feed, continuously.
Other important biosecurity measures like water sanitation by use of chemicals like hydrogen peroxide and chlorine in drinking water can help prevent water-borne bacterial diseases in poultry [36]. This will in the long run minimize the need for antibiotic administration and further reduce the risk of drug residues (in meat and eggs) and AMR.
Another important way that can help reduce the dependence of poultry farmers on antibiotics is the use of bacterins of the right strains of bacteria that are specifically enzootic to such geographical areas. This also calls for proper surveillance.
Phytobiotics are a wide range of plant-based compounds that could be incorporated into animal feed and they improve productivity. They are natural and do not leave residues in animal tissues as seen with antibiotics. They have antibacterial, anticoccidial, antifungal, antioxidant, and immunostimulant properties [37]. They penetrate and disintegrate the pathogen cell membrane resulting in the death of the pathogen via ion leakage. Phytobiotics such as oregano, thyme, or cinnamon show broad anti-bacterial activity against bacteria such as E.coli, Salmonella, and Clostridium spp.[37]. One of the areas where more research needs to be done in the use of phytobiotics in bacterial disease control is standardization of products to ensure consistent results.
Conclusion
The issue of multi-drug resistant avian bacterial isolates and high mortalities caused by these bacterial pathogens remains a major concern to stakeholders because of the economic implications and public and environmental health impact. Veterinarians and other animal health workers need to educate poultry farmers on the key measures they must adhere to to ensure minimal exposure of birds to bacterial pathogens. Improved farm biosecurity, water sanitation, feed sanitation (as in the use of feed-grade organic acids), vaccination against bacterial diseases, and use of phytobiotics and probiotics can help reduce farmers’ dependence on antibiotics.
Acknowledgment
Special thanks to Mrs Rose Fanto, Mrs Naomi Jerry Yahaya, Mrs Nancy Musa, Mrs Alheri Ponjul, and Mr Charibu Dishon for their roles in the daily recording of Clinical and laboratory findings.
Authors contributions
Oladele OO, Ameji NO, Agweche OS, Jambalang AR, Adanu AW, Durkwa HU, Agwom DM, and Haruna AM were involved in necropsy, documentation, and data analysis. Bitrus AA, Nnadi NE, were involved in bacterial isolation and characterization, and Lombin LH was involved in providing Clinic and laboratory facilities for handling the cases.
