Poultry products, including meat and eggs, represent an important means of meeting human needs for animal protein ². Population growth, increasing consumption, and rapid urbanization have contributed to a steady rise in the demand for poultry products. Poultry meat, particularly chicken meat, is the most popular type of white meat, and its consumption is expected to continue increasing over the next decade ³. Annual poultry production is projected to exceed 37 billion animals by 2050 ⁴. In Türkiye, poultry products supply a substantial share of basic nutritional needs and continue to expand within the livestock sector (Table 1) ⁵.

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Table 1: Poultry and egg production amounts in Turkey for 2023 and 2024

Among the most important factors threatening poultry production in Türkiye are flock-level poultry diseases, which can lead to substantial economic losses. Therefore, early diagnosis and the prevention of flock-related problems are of critical importance. In addition, the most frequently encountered bacterial agents causing disease in poultry include Salmonella spp., Escherichia spp., Clostridium spp., Staphylococcus spp., Campylobacter spp., Bacillus spp., and Listeria spp. These bacterial infectious agents may also cause disease in humans through poultry-derived food products. Thus, poultry diseases not only result in economic losses in poultry production but also pose serious public health concerns ^6-9.

Bacterial, viral, fungal, parasitic, and nutritional diseases that significantly affect productivity in poultry can largely be identified through necropsy findings and the macroscopic and microscopic examination of lesions. This is highly important for preventing major potential losses. To date, numerous studies have been conducted, and continue to be conducted, to improve and increase poultry production; therefore, updating the current body of knowledge remains essential for future studies ^10-12. The aim of this study was to evaluate poultry diseases observed in both small-scale and industrial poultry enterprises in our region and to obtain up-to-date data.

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Table 2: Information about the animals

Bacteriological Isolation and Phenotypic Identification: Lung, liver, and air sac samples collected from the birds were aseptically inoculated onto 5% sheep blood agar (Oxoid, United Kingdom) and incubated aerobically at 37°C for 24 hours. Colonies showing growth were subcultured onto MacConkey agar and Eosin Methylene Blue (EMB) agar (Oxoid, United Kingdom) and re-incubated under the same conditions. Gram staining, catalase, and oxidase tests were used for the phenotypic examination of the isolates.

For the isolation of Salmonella spp., 1 g of liver sample was weighed and subjected to pre-enrichment in 9 mL of Buffered Peptone Water (Merck, Darmstadt, Germany) at 37°C for 24 hours. After pre-enrichment, 0.1 mL of this culture was transferred into Rappaport-Vassiliadis broth (Merck, Darmstadt, Germany) and selectively enriched at 42°C for 24 hours. Subsequently, 10 µL from the Rappaport-Vassiliadis broth culture was streaked onto XLT4 agar (Merck, Darmstadt, Germany), and the plates were incubated aerobically at 37°C for 24 hours. Suspected colonies obtained were purified, and MacConkey agar, EMB agar, Gram staining, oxidase testing, and Triple Sugar Iron (TSI) agar were used for phenotypic identification.

Statistical Analysis: The collected data were classified according to disease type. Statistical analyses were performed using the SPSS software package (IBM SPSS Statistics for Windows, Version 22.0), employing Fischer's Exact Chi-square Test. The main effects and interactions of the data are presented as mean ± standard error. Statistical significance was set at p<0.05.

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Figure 1: Gross pathological findings in visceral organs. (A) Liver exhibiting multifocal to coalescing, irregular, pale-yellow necrotic foci scattered throughout the parenchyma (arrow). (B) Cecum characterized by multifocal necrotic lesions and abundant friable, yellow-white caseous material on the mucosal surface and within the lumen (star). (C–D) Heart with multifocal, irregular, pale-white to yellow necrotic foci extending into the myocardium. (E) Air sac containing adherent, opaque, yellow-white caseous exudate, consistent with airsacculitis (star). (F) Lung containing fibrinonecrotic, yellow-white caseous exudate on the pleural surface and within affected parenchymal areas (star). (G) Liver and heart showing multifocal pale discoloration associated with necrotic parenchymal lesions. (H) Pericardium displaying pale-yellow necrotic plaques and foci, consistent with fibrinonecrotic pericarditis (arrow).

Histopathological Findings:

Liver; In the liver, pseudoglandular arrangement of hepatocytes, subcapsular hemorrhages, periportal inflammatory cell infiltration, and fibrosis (Figure 2A), multifocal typhoid nodules (Figure 2F) were observed.

Cecum; In the cecum, diffuse inflammatory cell infiltration and congestion were detected (Figure 2B), multifocal typhoid nodules and diffuse lymphohistiocytic infiltrations were observed.

Pericarditis; Widespread lymphocytic infiltration was observed in the heart.

Heart; In the heart, subepicardial lymphohistiocytic infiltrations were observed (Figure 2C).

Airsacculitis: In the air sacs, randomly distributed lymphohistiocytic infiltrations and foci of caseous necrosis were observed (Figure 2D).

Lungs; The lungs exhibited diffuse congestion, perivascular edema, widespread heterophilic infiltration, and fibrin accumulation within the interstitial tissues (Figure 2E).

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Figure 2: Histopathological findings in visceral organs. (A) Liver exhibiting focal to multifocal hepatocellular necrosis, loss of hepatic cord architecture, cytoplasmic hypereosinophilia, karyorrhexis, karyolysis, and inflammatory cell infiltration (arrow). (B) Cecum characterized by diffuse transmural inflammatory infiltration, hemorrhage, mucosal necrosis, and luminal necrotic cellular debris (star). (C) Heart with diffuse lymphocytic myocarditis, including interstitial and perivascular lymphocytic infiltration separating myocardial fibers (arrow). (D) Air sac displaying lymphohistiocytic inflammation (arrow) and focal caseous necrosis composed of amorphous eosinophilic debris and degenerate inflammatory cells (star). (E) Lung characterized by diffuse vascular congestion and heterophil-rich inflammatory infiltration within the interstitium and air spaces, consistent with acute fibrinopurulent pneumonia (arrow). (F) Liver containing multifocal typhoid nodules composed of macrophages, heterophils, and necrotic cellular debris within the hepatic parenchyma (arrow).

Microbiological Findings: Microbiological examination revealed the isolation of E. coli from 9 air sac samples, Salmonella spp. from 3 liver samples, and Pasteurella spp. from 4 lung samples. The E. coli isolates produced pink to red colonies on MacConkey agar, consistent with lactose-positive characteristics, and exhibited colonies with dark centers and a greenish metallic sheen on EMB agar. On Gram staining, these isolates appeared as Gram-negative bacilli and were catalase-positive and oxidase-negative.

The Salmonella spp. isolates formed typical suspicious colonies with black centers on XLT4 agar and showed colorless colonies on MacConkey agar, consistent with lactose-negative characteristics. They were observed as Gram-negative bacilli on Gram staining and were catalase-positive and oxidase-negative. In addition, these isolates showed an alkaline slant/acid butt (K/A) reaction with H₂S production on TSI agar, consistent with glucose fermentation and the absence of lactose and sucrose fermentation.

The Pasteurella spp. isolates formed small, grayish-translucent, non-hemolytic colonies on blood agar and showed no growth on MacConkey agar. On Gram staining, they appeared as Gram-negative coccobacilli and yielded positive reactions for both catalase and oxidase tests.

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Table 3: Distribution of the lesions type

In the present research, Salmonella spp. was isolated from three cases of bacterial infections of the digestive system. The macroscopic and microscopic findings observed in these cases where Salmonella spp. was isolated are consistent with the literature. In this context, previous studies have also demonstrated that salmonellosis causes widespread areas of macroscopic necrosis in the liver and typhoid nodules at the microscopic level ¹⁴.

A macroscopic and microscopic examination revealed dilatation of the cecum, a significant quantity of necrotic material within the cecum, and necrotic pale areas were observed in the liver. These findings are consistent with those reported in other studies where histomoniasis (Histomonas meleagridis) on this subject ¹⁵. Furthermore, in the case where Marek's disease was suspected, widespread pale areas were observed macroscopically in the heart, and widespread lymphocytic infiltration was observed microscopically; these findings are consistent with those reported in previous cases ¹⁶.

A previous study conducted using data obtained from the Turkish Ministry of Agriculture and Forestry and the Turkish Statistical Institute (TÜİK) similarly reported that bacterial and parasitic diseases were the predominant causes of disease and that their frequency increased during the spring and summer seasons. Bacterial diseases are commonly encountered in poultry flocks due to inadequate ventilation, poor hygiene conditions, overcrowding, and insufficient implementation of infection control measures ¹⁷. Accordingly, it is essential to ensure adequate ventilation in poultry farms, avoid housing different animal species together, improve hygiene conditions, strengthen preventive measures against bacterial infections, and optimize nutritional management.

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