Sanitary disposal of contaminated organic material during recovery from an animal disease outbreak is costly and laborious. Characterizing the thermal stability of avian paramyxovirus type 1 (APMV-1; virulent APMV-1 strains cause Newcastle disease in poultry) will help inform risk assessments on the presence of viable virus on infected premises or in organic waste from infected premises. In some environments and housing types, heat may also be used as a decontamination method. Therefore, the objective of this study was to characterize the thermal stability (i.e., decimal reduction values [D values]) of APMV-1 in poultry litter. Virus inactivation was evaluated at seven temperatures from 10.0 C through 43.3 C, at 5.5 C intervals (50–110 F in 10 F intervals), using the I2 isolate of APMV-1, a vaccine strain known to be thermally stable. A high titer of virus (approximately 10⁸ 50% egg infectious doses) was added to wood shavings based, soiled chicken litter (poultry litter). Litter with both low and high moisture levels were evaluated. Samples were collected at different time intervals, and infectious virus was titrated in embryonated chicken eggs. At high temperatures (37.8 C–43.3 C), infectious virus could not be detected after 2–7 days, whereas at lower temperatures (10 C–21.1 C), it took up to 112 days for virus to decrease to undetectable levels. Furthermore, the D values were almost always shorter in the high moisture litter.

Necrotic enteritis (NE) is an important intestinal disease of commercial poultry associated with poor performance, high mortality, and significant economic loss. In this case report, a novel presentation of NE is described in young broilers. Initially, affected farms presented with a moderate increase in mortality at or before 19 days of age. Farms experiencing the disease syndrome belonged to two complexes of the same company. However, all farms sourced chicks from the same hatchery. Farm postmortem examinations revealed moderate to severe enteritis of the upper small intestine characterized by multifocal, irregular, plaque-like, mucosal ulcerations. Additionally, thinning of the intestinal wall with consequential distension and ballooning and a necrotic, pseudomembranous layer covering the mucosa were observed in some birds. Clinically affected birds were submitted to the Poultry Research and Diagnostic Laboratory at Mississippi State University for further evaluation. Birds were between 5 and 11 days of age and presented with similar gross lesions. Anaerobic culture was performed, and Clostridium perfringens was isolated from affected intestinal sections. Environmental sampling at the hatchery was also performed to evaluate the presence and load of clostridial organisms. Clostridium perfringens was isolated from samples collected in the egg room, hatchers/hatch halls, separator room, processing room, and transport trucks. Furthermore, VITEK^® mass spectrometry matrix-assisted laser desorption ionization time-of-flight results indicated a 99.9% genetic relatedness between hatchery and live bird isolates, demonstrating an epidemiologic link between clinically affected birds and the hatchery as a point source. This novel presentation of C. perfringens in young broilers warrants attention because proper development of the gastrointestinal tract in the first weeks of life is critical for competitive production in the modern broiler.

Vitamin D is a hormone that can be ingested or synthesized in the body when skin is exposed to ultraviolet radiation (UV), typically from sunlight. In captivity, birds with no sunlight exposure may develop vitamin D deficiencies that may contribute to hypocalcemic conditions, even when fed a diet supplemented with vitamin D. An initial pilot study with Hispaniolan Amazon parrots (Amazona ventralis) conducted approximately 18 mo prior indicated there were significant differences in the 25-hydroxyvitamin D (vit D) plasma levels between the resident parrots (indoor-only housing) and a new group of historically outdoor-housed parrots (new parrots) 5 days after the arrival of the latter at our institution. The goals of this study were to determine if vit D, ionized calcium (Ca²⁺), and ionized magnesium (Mg²⁺) levels changed from baseline values (taken 18 mo prior) in the new birds as well as to compare those values to those of the resident birds over time. The treatment was a change in husbandry for the new parrots (no UV exposure and diet as provided for the resident parrots). To accomplish this, the authors compared vit D levels in the same two groups of birds that were fed the same vit D–fortified diet and given no access to natural or artificial UV light exposure for 18 mo. The resident parrots (N = 9) had been housed indoors for approximately 20 yr with no exposure to natural or supplemented UV light. The second group of birds (new parrots; N = 8) had been housed outdoors prior to the initiation of the pilot study in 2016 and were fed a similar—but not identical—diet prior to their arrival. Plasma samples were sent to the Michigan State University Diagnostic Center for Population and Animal Health for analysis. Test results demonstrated differences between the two groups of parrots, largely attributed to the decrease in vit D plasma levels in the new parrots over time to values equivalent to those measured in the resident birds. Differences were seen in plasma Ca²⁺, while no differences were demonstrated relative to Mg²⁺. We discuss these findings and suggest that plasma vit D levels decrease in the absence of UV light, even when animals are maintained on a vit D–fortified and balanced diet.

Repeated cases of low pathogenic influenza A/H9N2 virus (IAV/H9N2) have been reported in commercial chickens since its emergence in 1998 in Pakistan. However, recently increased mortality and severe respiratory complications under field conditions have been noticed, suggesting concomitant influenza infections with respiratory viral and/or bacterial pathogens. Therefore, the present study aimed to investigate the presence of IAV/H9N2 coinfecting with multiple viral and bacterial pathogens in broiler chicken flocks. We surveyed 60 broiler flocks with respiratory signs from March through July 2019 in Punjab, Pakistan. Suspected flocks were screened for the presence of IAV using a lateral-flow device. Tracheal, cloacal, and bone marrow samples were collected and further tested for seven viral agents (chicken anemia; Newcastle disease; infectious bronchitis; infectious laryngeotracheitis [ILT]; and IAV subtypes H9, H7, and H5) and three bacterial agents (Mycoplasma gallisepticum; Mycoplasma synovae; Ornithobacterium rhinotracheale [ORT]) using PCR assays. Upon initial screening for IAV, 35/60 (58.3%) flocks tested positive. The coinfection of IAV/H9N2 with other pathogens was detected in 25 (71.4%) flocks and only IAV/H9N2 was detected in 10 (28.6%) flocks out of total positive IAV flocks (n = 35). IAV subtypes H5 and H7, ILT, and ORT were not detected throughout the study period. The detection rate of double, triple, and quadruple combinations of coinfections with IAV/H9N2 were 37% (13 flocks), 26% (9 flocks), 9% (3 flocks), respectively. Higher average mortality (28.5%) was found in broiler chicken flocks coinfected with viral and/or bacterial pathogens than in flocks where only H9 low pathogenic IAV/H9N2 was detected (20.8%). In conclusion, higher circulation of IAV/H9N2 with other viral and bacterial pathogens may contribute to higher production and economic losses at the farm level.

Infectious bronchitis virus (IBV) is a major pathogen in poultry. The genotypes of IBV vary considerably, and their antigenicity may differ. Nationwide surveillance in South Korea was performed to determine the prevalence and distribution of IBV and its genotypes. By both active and passive surveillance, a total of 939 samples were collected and tested for IBV detection by pathogen-specific reverse transcriptase–PCR. IBV RNA-positive samples were inoculated in embryonated eggs for virus isolation. IBV was genotyped and analyzed phylogenetically based on a partial nucleotide sequence of the S1 gene. A total of 114 IBV strains were isolated; 34 (30.9%) of the 110 samples obtained by passive surveillance, and 80 (9.7%) of the 829 samples obtained by active surveillance, were positive. Most IBVs in both groups were isolated from broilers. Five genotypes (QX-like, B4-like, KM91-like, K40/09-like, and 20AD17-like) were observed in South Korea, with the QX-like genotype being the most common, and the 20AD17-like genotype being a novel genotype. These findings will help to maximize protection against IBV infection by providing a reference for the selection of an avian vaccine for IBV in South Korea.

Necrotic enteritis (NE) is a serious disease of chickens and turkeys that causes significant economic losses to the poultry industry. On the basis of studies in chickens, Clostridium perfringens type G is considered by many to be the cause of NE in poultry. However, studies on isolates from Finnish and Italian turkeys with NE revealed that the vast majority were C. perfringens type A, and very few were C. perfringens type G. We therefore examined 74 C. perfringens isolates from U.S. turkeys with NE; 98% were type A and only 1% was type G. This result confirms that different C. perfringens types are involved in NE in turkeys when compared with chickens. We also examined the turkey isolates for other toxin genes associated with enteritis in various animal species, namely tpeL, cpb2, cpe, netE, netF, and netG. The tpeL gene, which has been associated with enhanced virulence of C. perfringens in chickens, was only found in 1% of turkey NE isolates. The cpe gene, which encodes C. perfringens enterotoxin (a major cause of food poisoning and non-foodborne C. perfringens-mediated diarrhea in humans) was also found in only 1% of our turkey NE isolates. Although cpb2, which encodes for the beta2 toxin, was found in 73% of our NE isolates, it has also been found in similar percentages of isolates from turkeys with normal intestine. The netE, netF, and netG genes were not detected among our C. perfringens isolates from turkeys.

Two 7-wk-old broiler chickens presented with uniformly black livers upon postslaughter examination, while all other organs as well as their carcasses were grossly normal. No clinical signs were reported by the field veterinarian prior to slaughter. Other broiler chickens within the same flock were unaffected. Microscopically, the liver exhibited variably sized, globoid concrements that were dark brown to green-brown and birefringent under polarized light. Ultrastructurally, concrements consisted of radially arranged electron-dense crystal spicules. Concrements were located in hepatocytes, within ecstatic bile canaliculi, or surrounded by small clusters of macrophages. Liquid chromatography assay determined the presence of protoporphyrin IX in the affected liver.

A 3-yr-old Ameraucana hen was received for postmortem examination following a 1-day history of lethargy and death. Gross lesions observed during necropsy were limited to pulmonary congestion and a small clump of egg yolk material in the oviductal lumen. On histopathology, there was a necrotizing salpingitis of the infundibular and isthmus mucosa with amphophilic, intranuclear inclusion bodies in superficial epithelial cells. Transmission electron microscopy identified the intranuclear inclusions as aggregates of adenovirus virions. Fowl adenovirus (FAdV) type A was identified with PCR and sequencing. Although the cause of death was not determined in this case, this is the first report of FAdV type A–associated salpingitis in a hen.

Avian influenza (AI) is a zoonotic disease that will likely be involved in future pandemics. Because waterbird movements are difficult to quantify, determining the host-specific risk of Eurasian-origin AI movements into North America is challenging. We estimated relative rates of movements, based on long-term evolutionary averages of gene flow, between Eurasian and North American waterbird populations to obtain bidirectional baseline rates of the intercontinental movements of these AI hosts. We used population genomics and coalescent-based demographic models to obtain these gene-flow–based movement estimates. Inferred rates of movement between these continental populations varies greatly among species. Within dabbling ducks, gene flow, relative to effective population size, varies from ∼3 to 24 individuals/generation between Eurasian and American wigeons (Mareca penelope and Mareca americana) to ∼100–300 individuals/generation between continental populations of northern pintails (Anas acuta). These are evolutionary long-term averages and provide a solid foundation for understanding the relative risks of each of these host species in potential intercontinental AI movements. We scale these values to census size for evaluation in that context. In addition to being AI hosts, many of these bird species are also important in the subsistence diets of Alaskans, increasing the risk of direct bird-to-human exposure to Eurasian-origin AI virus. We contrast species-specific rates of intercontinental movements with the importance of each species in Alaskan diets to understand the relative risk of these taxa to humans. Assuming roughly equivalent AI infection rates among ducks, greater scaup (Aythya marila), mallard (Anas platyrhynchos), and northern pintail (Anas acuta) were the top three species presenting the highest risks for intercontinental AI movement both within the natural system and through exposure to subsistence hunters. Improved data on AI infection rates in this region could further refine these relative risk assessments. These directly comparable, species-based intercontinental movement rates and relative risk rankings should help in modeling, monitoring, and mitigating the impacts of intercontinental host and AI movements.

Newcastle disease virus (NDV) can infect approximately 250 avian species and causes highly contagious Newcastle disease (ND) in domestic poultry, leading to huge economic losses. There are three different pathotypes of NDV, i.e., lentogenic, mesogenic, and velogenic. Wild resident (wild) and migratory birds are natural reservoirs of NDV and are believed to play a key role in transmitting the virus to domestic poultry. The present study was conducted to determine the prevalence of NDV in wild and migratory birds in the state of Haryana, India, during two migratory seasons (2018–19 and 2019–20). In total 1379 samples (1368 choanal swabs and 11 tissue samples) were collected from live (n = 1368) or dead birds (n = 4) belonging to 53 different avian species. These samples belonged to apparently healthy (n = 1338), sick (n = 30), and dead (n = 4) birds. All samples were tested for NDV by real-time reverse transcription-PCR using M gene specific primers and probe. Of the 1379 samples, 23 samples from wild birds [Columba livia domestica (n = 12, 52.17%), Pavo cristatus (n = 9, 39.13%), and Psittaciformes (n = 2, 8.69%)] were found positive for NDV. Only one of the 23 samples (from P. cristatus) was positive for F gene, indicating it to be a mesogenic/velogenic strain. These results indicate that both lentogenic and velogenic strains of NDV are circulating in wild birds in Haryana and that further studies are needed to characterize NDV strains from wild/migratory birds and domestic poultry to determine the extent of virus transmission among these populations. This study considers the disease transmission risk from domestic pigeons and parrots to commercial poultry and vice versa, and the results emphasize the need for strict biosecurity strategies to protect commercial poultry in the region.

Newcastle disease viruses (NDVs) in Afghanistan were isolated from three chicken farms and identified using a hemagglutination test and reverse transcription-polymerase chain reaction assay. Three isolates from each farm were sequenced to characterize the part of their fusion protein gene around the cleavage site. The characteristics of the fusion protein genes of the three isolates shown by phylogenic analysis indicated that the isolates were velogenic, belonged to the class II subgenotype VII 1.1, and were closely related to an identified Chinese NDV isolate. To our knowledge, this is the first time that NDV isolates from Afghanistan have been partially sequenced.

Aislamiento, identificación y caracterización molecular del virus de la enfermedad de Newcastle de brotes de campo en pollos en Afganistán

Se aislaron virus de la enfermedad de Newcastle (NDV) en Afganistán de tres granjas de pollos y se identificaron mediante una prueba de hemaglutinación y un ensayo de transcripción reversa y reacción en cadena de la polimerasa. Se secuenciaron tres aislados de cada granja para caracterizar la parte correspondiente al gene de la proteína de fusión alrededor del sitio de disociación. Las características de los genes de la proteína de fusión de los tres aislamientos mostrados por el análisis filogenético indicaron que los aislamientos eran velogénicos, pertenecían a la clase II subgenotipo VII 1.1 y estaban estrechamente relacionados con un aislado del virus de Newcastle identificado en China. Hasta donde se sabe, esta es la primera vez que los aislamientos del virus de Newcastle de Afganistán se han secuenciado parcialmente.

Fowl adenoviruses cause three economically important diseases in broiler chicken flocks: hepatitis-hydropericardium syndrome (HHS), inclusion body hepatitis (IBH), and adenoviral gizzard erosion. IBH has not been considered a serious threat in northeast Iran since the last decade, because no major effect on flock performance has been noticed along with a low mortality rate. During this period, all the sporadic IBH outbreaks have also been investigated for HHS without finding any confirmed case. In March 2021, a 15-day-old commercial broiler flock in northeast Iran showed a 50% mortality rate, and birds underwent postmortem examination, histopathology, molecular testing, and phylogenetic analysis for possible disease agents. Typical gross lesions of HHS were observed postmortem that included hydropericardium with an unusual accumulation of jelly-like and straw-colored fluid in the pericardial sac (without right ventricular failure); petechial or ecchymotic hemorrhages on the myocardium, myocardial valves, and endocardium; and discolored and mottled liver along with small white foci and petechial or ecchymotic hemorrhages. Histopathologic analysis showed necrosis of hepatocytes and basophilic inclusion bodies in the livers. The molecular tests performed for detection of fowl adenovirus (FAdV), H5 avian influenza virus, Newcastle disease virus, avian infectious bronchitis virus (IBV), H9N2, chicken infectious anemia virus (CIAV), infectious bursal disease (IBD) virus, Marek's disease virus, Ornithobacterium rhinotracheale, Mycoplasma gallisepticum, and Mycoplasma synoviae turned out positive for FAdV, CIAV, IBD vaccine virus, and IBV serotypes 793B and variant I. The phylogenetic tree based on the hexon gene loop 1 demonstrated a FAdV serotype 4 (FAdV-4) that was identical to Pakistani isolate PARC-1/98. Because it was the first detection of a FAdV-4 in Iran, the stamping out program was applied immediately on the basis of HHS gross lesions and positive PCR reaction on pericardial jelly-like fluid. It seems that this eradication strategy was successful because no outbreaks were noticed for 2 mo after the initial outbreak. It was concluded that the use of gross pathologic baselines, quick diagnosis of disease, and close collaboration between governmental and private sectors were the critical factors that helped locally control the first occurrence of HHS in Iran.

Reporte de caso- Primera presentación del síndrome de hepatitis-hidropericardio (HHS) en Irán y medidas efectivas de control aplicadas en la parvada comercial de pollos de engorde afectada.

Los adenovirus del pollo causan tres enfermedades económicamente importantes en las parvadas de pollos de engorde: síndrome de hepatitis-hidropericardio (HHS), hepatitis con cuerpos de inclusión (IBH) y erosión de la molleja por adenovirus. La hepatitis con cuerpos de inclusión no se ha considerado una amenaza grave en el noreste de Irán desde la última década, porque no se ha observado un efecto importante en el rendimiento de la parvada junto con una baja tasa de mortalidad. Durante este período, todos los brotes esporádicos de hepatitis con cuerpos de inclusión también han sido analizados para el síndrome de hepatitis-hidropericardio sin encontrar ningún caso confirmado. En marzo del 2021, una parvada comercial de pollos de engorde de 15 días de edad en el noreste de Irán mostró una tasa de mortalidad del 50 % y las aves se sometieron a un examen post mortem, histopatología, pruebas moleculares y análisis filogenético para detectar posibles agentes patógenos. Se observaron lesiones macroscópicas post mortem típicas del síndrome de hepatitis-hidropericardio que incluían hidropericardio con una acumulación inusual de líquido gelatinoso y de color pajizo en el saco pericárdico (sin insuficiencia ventricular derecha); hemorragias petequiales o equimóticas en el miocardio, válvulas miocárdicas y endocardio; e hígado decolorado y moteado junto con pequeños focos blancos y hemorragias petequiales o equimóticas. El análisis histopatológico mostró necrosis de hepatocitos y cuerpos de inclusión basófilos en los hígados. Se realizaron pruebas moleculares para la detección de adenovirus del pollo (FAdV), virus de la influenza aviar H5, virus de la enfermedad de Newcastle, virus de la bronquitis infecciosa aviar, virus de influenza tipo H9N2, virus de la anemia infecciosa de los pollos, virus de la enfermedad infecciosa de la bolsa, virus de la enfermedad de Marek, Ornithobacterium rhinotracheale, Mycoplasma gallisepticum y Mycoplasma synoviae con resultados positivos para adenovirus del pollo, virus de la anemia infecciosa, virus vacunal de Gumboro y virus de la bronquitis infecciosa serotipos 793B y variante I. El árbol filogenético basado en la asa 1 del gene del hexon demostró la presencia del serotipo 4 del adenovirus del pollo (FAdV-4) que era idéntico al aislamiento pakistaní PARC-1/98. Debido a que fue la primera detección de un adenovirus de pollo serotipo 4 en Irán, el programa de despoblación sanitario se aplicó de inmediato sobre la base de lesiones macroscópicas del síndrome de hepatitis-hidropericardio y por reacción de PCR positiva en el líquido pericárdico gelatinoso. Parece que esta estrategia de erradicación tuvo éxito porque no se notaron brotes durante dos meses después del brote inicial. Se concluyó que el uso de líneas base de patología macroscópica, el diagnóstico rápido de la enfermedad y la estrecha colaboración entre los sectores gubernamental y privado fueron los factores críticos que ayudaron a controlar localmente la primera presentación del síndrome de hepatitis-hidropericardio en Irán.Key words: hepatitis-hydropericardium syndrome, FAdV-4, control measures, Iran

The poultry industry needs alternatives to antibiotics, as there are growing public concerns about the emergence of antimicrobial resistance owing to antimicrobial use in animal production. We have reported that the administration of neonatal chicks with synthetic DNA oligodeoxynucleotides containing unmethylated cytosine guanine dinucleotide (CpG) motifs (CpG-ODN) can protect against bacterial pathogens in chickens. The objective of this study was to compare the immunoprotective effects of CpG-ODN and probiotics against Escherichia coli infection vs. commonly used therapeutic antibiotics. Day-old broiler chicks were divided into five groups (n = 35/group; 30 for the challenge experiment and 5 for the flow cytometry analysis). The chicks in Group 1 received a single dose of CpG-ODN by the intramuscular route on day 4 (D4) posthatch (PH), and Group 2 received drinking water (DW) with a probiotic product (D1–D15 PH, DW). The Group 3 chicks received tetracycline antibiotics during D9–D13 in DW; the Group 4 chicks got sodium sulfamethazine on D9, D10, and D15 PH in DW; and the Group 5 chicks were administered intramuscular (IM) saline D4 PH, DW. We challenged all the groups (n = 30/group) with E. coli (1 × 10⁵ or 1 × 10⁶ colony-forming units/bird) on D8 PH through the subcutaneous route. Our data demonstrated that the CpG-ODNs, but not the probiotics, could protect neonatal broiler chickens against lethal E. coli septicemia, as would the tetracycline or sodium sulfamethazine. The flow cytometry analysis (n = 5/group) revealed enrichment of immune cells in the CpG-ODN group and a marked decrease in macrophages and T-cell numbers in antibiotics-treated groups, indicating immunosuppressive effects. Our data showed that, like therapeutic antibiotics, CpG-ODNs reduced clinical signs, decreased bacterial loads, and induced protection in chicks against E. coli septicemia. Unlike therapeutic antibiotics-induced immunosuppressive effects, CpG-ODN caused immune enrichment by increasing chicken immune cells recruitment. Furthermore, this study highlights that, although therapeutic antibiotics can treat bacterial infections, the ensuing immunosuppressive effects may negatively impact the overall chicken health.

Comparación de antibióticos terapéuticos, probióticos y CpG-ODN sintéticos en su eficacia protectora contra la infección letal por Escherichia coli y el impacto en el sistema inmunológico en pollos de engorde recién eclosionados.

La industria avícola necesita alternativas a los antibióticos ya que existe una creciente preocupación pública sobre la aparición de resistencia a los antimicrobianos debido a su uso en la producción animal. Se ha informado que la administración de oligodesoxinucleótidos de ADN sintético que contienen motivos de dinucleótidos de citosina guanina (CpG) no metilados (CpG-ODN) a pollitos recién eclosionados puede proteger contra patógenos bacterianos en pollos. El objetivo de este estudio fue comparar los efectos inmunoprotectores de CpG-ODN y de los probióticos contra la infección por Escherichia coli frente a los antibióticos terapéuticos de uso común. Los pollos de engorde de un día se dividieron en cinco grupos (n = 35/grupo; 30 para el experimento de desafío y 5 para análisis de citometría de flujo). Los pollitos del Grupo 1 recibieron una dosis única de CpG-ODN por vía intramuscular el día 4 (D4) después de la eclosión (PH), y el Grupo 2 recibió agua potable (DW) con un producto probiótico del día uno al quince después de la eclosion en agua de bebida. Los pollitos del Grupo 3 recibieron tetraciclina durante los días nueve a trece (D9–D13) en agua de bebida (DW9; los pollitos del Grupo 4 recibieron sulfametazina de sodio en los días nueve, diez y 15 (D9, D10 y D15) después de la eclosion en agua de bebida; ya los pollitos del Grupo 5 se les administró solución salina intramuscular (IM) al día cuatro después de la eclosión en agua de bebida. Se desafiaron todos los grupos (n = 30/grupo) con E. coli (1 × 10⁵ o 1 × 10⁶ unidades formadoras de colonias/ave) en el día ocho después de la eclosión por vía subcutánea. Nuestros datos demostraron que los CpG-ODN, pero no los probióticos, pudieron proteger a los pollos de engorde recién eclosionados contra la septicemia letal por E. coli, al igual que la tetraciclina o la sulfametazina sódica. El análisis de citometría de flujo (n = 5/grupo) reveló un enriquecimiento de células inmunes en el grupo CpG-ODN y una marcada disminución en el número de macrófagos y células T en los grupos tratados con antibióticos, lo que indica efectos inmunosupresores. Nuestros datos mostraron que, al igual que los antibióticos terapéuticos, los CpG-ODN redujeron los signos clínicos, disminuyeron las cargas bacterianas e indujeron protección en los pollitos contra la septicemia por E. coli. A diferencia de los efectos inmunosupresores inducidos por antibióticos terapéuticos, los CpG-ODN provocaron un enriquecimiento inmunitario al aumentar el reclutamiento de células inmunitarias de pollo. Además, este estudio destaca que, aunque los antibióticos terapéuticos pueden tratar las infecciones bacterianas, los efectos inmunosupresores resultantes pueden tener un impacto negativo en la salud general de los pollos.