In the domain of avian species, the ostrich (Struthio camelus) has long intrigued humanity, with its significance extending into the global livestock market. The rapid growth of ostrich farming has led to a flourishing industry, producing valuable products, including high-quality feathers, lean meat, premium leather, and nutritious eggs, positioning it as an appealing alternative for numerous countries.1 Ostrich meat, classified as poultry, offers a mild flavor similar to beef and is gaining popularity in markets due to its nutritional benefits. With a high protein content (22.2%), low fat (1.6%), and lower cholesterol (33.8 mg per 100 g) compared to turkey and beef, it presents a healthier red meat alternative. Its tenderness and digestibility make it particularly appealing to health-conscious consumers.2 while ostrich production remains a niche sector globally (about 2 billion dollars annually), it is economically significant, especially in terms of meat, leather, and luxury goods. Its value is most prominent in regions where ostrich farming is well established, particularly South Africa, but the industry is also growing in other parts of the world especially Egypt, contributing to global trade in these products.
Additionally, these remarkable birds are frequently exhibited in zoos and private parks, captivating audiences globally. However, as the ostrich industry expands, it is crucial to recognize the potential risks associated with direct contact with these birds and their products, particularly concerning the transmission of zoonotic diseases. With the increasing demand for ostrich-derived products, prioritizing the understanding and mitigation of these risks is essential for ensuring a safe and sustainable industry.1
Egypt’s rich historical narrative includes the African ostrich, a species that once thrived in the region. However, a combination of climate change and overhunting resulted in a significant decline, leading to the species’ extinction in the area by the 1990s.3 Remarkably, the ostrich has made a successful return to Egypt in the 21st century as a domesticated species flourishing on farms. Presently, Egypt’s ostrich industry is experiencing a resurgence, with an increase in the number of farms dedicated to raising these birds, representing a hopeful prospect for the long-term sustainability of the species.4
Ostriches, similar to other avian species, are susceptible to various infectious agents; however, they do not possess unique diseases exclusive to their species. Instead, they are more vulnerable to bacterial pathogens such as Escherichia coli, Salmonella spp., Clostridium spp., and Campylobacter spp., which can severely impact their digestive and respiratory systems.5 The environment plays a significant role in the transmission of these pathogens, with contaminated vegetation, soil, and water sources posing risks, particularly to young ostriches from an early age. While adult ostriches generally exhibit resilience to health issues, juveniles are particularly susceptible to infections caused by hemolytic E coli, which can lead to severe consequences if not addressed.6
Extraintestinal pathogenic E coli (ExPEC) in chickens causes a variety of systemic diseases, with the most common being avian colibacillosis, septicemia, and reproductive infections. These bacteria are equipped with virulence factors that allow them to spread throughout the body, leading to severe illness. Avian pathogenic E coli (APEC) is considered an ExPEC and exhibits a distinct pathogenic profile, differing from its enteric relatives in its ability to induce a range of extraintestinal diseases, notably respiratory and systemic infections. As the primary causative agent of avian colibacillosis, APEC initiates a complex disease process, starting with an upper respiratory infection that can escalate into an invasive phase, affecting critical tissues such as the liver, heart, spleen, and the air sac system. The disease is characterized by a variety of inflammatory responses, including airsaculitis, perihepatitis, pericarditis, peritonitis, salpingitis, and synovitis, among other extra-intestinal manifestations that highlight the complexity of this avian disease.7 The presence of E coli in ostrich products poses a significant risk of commercial repercussions, potentially leading to trade restrictions on meat and other products.8 Furthermore, it presents a serious public health concern, as E coli is a common foodborne pathogen with extensive implications for human health, as discussed by Zaki.9
This investigation aimed to identify and isolate E coli strains from ostriches that had succumbed to disease, followed by comprehensive biochemical and serological characterization of the isolated pathogens. The study also sought to evaluate the pathogenic potential of these E coli isolates in ostriches aged 1 to 12 weeks, with a particular focus on elucidating the presence of virulence factors that contribute to their disease-causing capabilities.
Methods
Ostrich farms locality
A comprehensive study was conducted between March and December 2023 to isolate and identify APEC in ostrich farms suspected to be affected by colibacillosis. The study encompassed a total of seven farms, with bird ages from 1 to 12 weeks. The farm capacities varied from 2,000 to 5,000 birds per farm. The farms were located in four governorates in Egypt, specifically New Valley, Sharkia, Ismailia, and Dakahlia.
Sample collection
Fifty dead chicks were subjected to necropsy to identify different pathological lesions. Then, 175 tissue samples were obtained: 25 samples from each of the “liver, spleen, heart, lung, kidney, and intestine, as well as breast muscles of ostriches” (1 to 12 weeks of age) exhibiting symptoms of weight loss, diarrhea, and respiratory distress. The specimens were obtained from Islamic slaughtered birds.10 The specimens were sent to a bacteriological laboratory in an ice box under perfect aseptic conditions as soon as feasible. The laboratory was a biosafety level-2 facility that was designed to safely handle biological agents that pose a moderate risk to both laboratory personnel and the surrounding environment.
Bacteriological examination
Escherichia coli isolation and identification protocol
Aseptically collected tissue from ostrich lung, liver, spleen, meat, and kidney were enriched in nutrient broth (Oxoid) at 37 °C for 24 to 48 hours to facilitate E coli growth.
Selective isolation
Enriched broth was then streaked onto MacConkey agar (Oxoid) and eosin methylene blue agar (Oxoid) media, which selectively support the growth of Gram-negative Enterobacteriaceae and E coli, respectively. The inoculated media were incubated aerobically at 37 °C for 24 to 48 hours.
Colony characterization and confirmation
The resulting colonies were described based on their morphological and biochemical properties. Escherichia coli colonies exhibited distinct characteristics, including a diameter of 2 to 3 mm a light pink color on MacConkey agar, and a shiny metallic green color on eosin methylene blue agar. Further confirmation was achieved through a battery of biochemical tests, including oxidase, catalase, urease, hydrogen sulfide production in a triple sugar iron, citrate utilization, motility, and hemolysis on blood agar.9
Serological identification of E coli
The serological identification of E coli isolates was achieved using the slide agglutination technique, as described by Asmaa et al.11 The technique involved mixing the bacterial cultures with specific antisera on a glass slide, followed by gentle agitation to facilitate agglutination. The presence of agglutination indicated a positive reaction, confirming the identity of the isolates.
Incidence of APEC differentiated using multiplex PCR
Detection of virulence-associated genes in E coli O27 isolates
The virulence potential of E coli O27 isolates was assessed by screening for the occurrence of 8 virulence-associated factors: astA, iss, irp2, papC, iucD, tsh, vat, and cva/cvi. Bacterial DNA was taken out from pure cultures by a commercial DNA purification kit (Qiagen, Germany). Specific primers for each virulent gene were designed and synthesized by Metabion (Germany), and their sequences are provided (Supplementary Table S1).12 PCR reactions were achieved in a 25 μL master mix has Emerald Amp Max PCR Master Mix (Takara), primers, and template DNA. The reactions were cycled using a Biometra T3 thermal cycler.
Histopathological inspection
Lungs, trachea, liver, spleen, kidneys, esophagus, proventriculus, and intestines samples were directly fixed in neutral buffered formalin 10%, washed, dehydrated, cleared, and embedded in paraffin. Paraffin blocks were sectioned at 4- to 5-μm thickness and stained with H&E consistent with Elbarbary et al.13 Slides were inspected under a light microscope (Leika DM500).
Ethical approval
The study protocol was approved by the Ethics Committee of the Faculty of Veterinary Medicine, Aswan University No. 12-02-2023.
Results
Clinical signs
Diarrhea was the most common and obvious sign, which was severe, watery yellowish diarrhea. The infected ostriches may appear lethargic, depressed, and weak due to dehydration and electrolyte imbalances caused by diarrhea. Also, ostriches often have a reduced or complete loss of appetite, leading to weight loss, dehydration, and poor body condition. In more severe cases, infections spread to the respiratory system, causing pneumonia and breathing difficulties. The morbidity rate was 36%, and the mortality rate was 7.6%.
Gross pathological findings
In 50 young chicks; the yolk sac was fully regressed, swollen, and enlarged yolk sac The yolk sac contents thickened, discolored, and ruptured (12/50; Figure 1). The lungs appeared congested, edematous, and consolidated, indicating the presence of pneumonia. Focal or diffuse areas of consolidation and discoloration (eg, greyish or yellowish) were visible on the lung surface with thickening of air sacs (22/50). The intestines appeared edematous, hyperemic, and hemorrhagic. Intestinal walls were thickened and the lumen may contain excessive, watery, or mucoid contents. Focal areas of necrosis or ulceration were detected along the intestinal tract (27/50). Also, enlarged and congested liver, spleen, and kidneys were seen (15/50). The morbidity rate was 36%, and the mortality rate was 7.6%.
A—Ostrich (3 weeks old) showing unabsorbed yolk sac (arrow). B—Ostrich (4 weeks old) showing thickening of air sac and congested lung (arrow). C—Ostrich (6 weeks old) showing congestion and distention of the intestine.
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.09.0280
Accordingly, to the gross findings the study analyzed 175 tissue samples (liver, spleen, heart, lung, kidney, and intestine, as well as breast muscles) and found that 52.5% (92 samples) tested positive for E coli. The highest prevalence was observed in the liver (10.8%), followed by the spleen and intestine (8% and 9.1%, respectively). The lowest prevalence was found in kidney (5.1%) and meat (3.4%) samples (Supplementary Table S2).
Serotypes and virulence-associated genes
Further investigation of the E coli isolates had shown a diverse range of serotypes. A total of 25 E coli isolates were from various tissue specimens of diseased and dead ostriches, and their serotypes were determined. The results are provided (Table 1).
Serotyping of Escherichia coli isolated from examined tissue specimens and their detected numbers.
| O serotype | Types of tissues | No. of isolates | Isolation (%) |
|---|---|---|---|
| O27 | Liver, spleen, lung, heart, breast muscles | 7 | 28 |
| O44 | Liver, kidney, breast muscles | 3 | 12 |
| O78 | Liver, lung, breast muscles, intestine | 5 | 20 |
| O103 | Liver, lung | 2 | 8 |
| O106 | Liver | 1 | 4 |
| O142 | Liver | 1 | 4 |
| O153 | Lung | 1 | 4 |
| O158 | Liver, intestine | 2 | 8 |
| O164 | Intestine | 1 | 4 |
| O untyped | Intestine | 2 | 8 |
| Total | 25 | 100 |
The most common serotype identified was O27, which was isolated from five different tissue types (liver, spleen, lung, heart, and meat) and accounted for 28% of the total isolates. The O78 serotype was the second most prevalent, isolated from four tissue types (liver, lung, meat, and intestine) and representing 20% of the total isolates. The O44 serotype was isolated from three tissue types (liver, kidney, and meat) and accounted for 12% of the total isolates. Other serotypes identified included O103, O106, O142, O153, O158, and O164, each accounting for 4% to 8% of the total isolates. Two isolates from the intestine (8%) remained untyped.
One strain, APEC O27, was found to carry 6 virulence-related genes, astA, iss, papC, iucD, vat, and cva/cvi, out of 7 isolates of the E coli O27 serotype, according to the findings of a PCR test for virulence-associated genes (Figure 2).
Agarose gel electrophoresis showing positive amplification of virulence-associated genes of Escherichia coli strain by multiplex PCR. Lane 1 shows 2 virulence-associated genes (irp2 and iucD). Lane 2 shows 2 virulence-associated genes (irp2 and tsh). Lane 3 shows E. coli-O27 had 6 virulence-related genes (astA, iss, papC, iucD, vat, and cva/cvi). Lane –ve shows the control negative. M = 100-bp ladder.
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.09.0280
Microscopic findings
Liver
The most constituent lesion was hepatocellular degeneration, in which swollen and vacuolated hepatocytes, indicated cellular degeneration. There were focal areas of hepatocellular necrosis, with pyknotic or karyorrhectic nuclei. Infiltration of the liver parenchyma by inflammatory cells, such as heterophils may be revealed with proliferation and hyperplasia of the bile ducts. Also, vascular changes were detected as congestion and dilation of the sinusoids and central veins. These microscopic changes lead to disruption of the normal hepatic architecture (Figure 3).
Photomicrograph of different organs (liver [A to C], kidneys (C, D, and G), and heart [E and F]). A—Severe vacuolar degeneration all over hepatic parenchyma (HP) especially around central veins (CV) and severely congested blood vessels (arrows) (H&E scale bar. 200 μm). B—Focal area of fatty degeneration (FD) with severely congested blood vessels (BV) (H&E scale bar, 50 μm). C—Diffuse interstitial haemorrhage (arrows) (H&E scale bar 200 μm). D and G—degeneration of convoluted tubules (CT) with pycnotic nuclei (arrows; D) some glomeruli showing degeneration (G; H&E scale bar 50 μm). E—Mild vascular congestion (arrows; H&E scale bar, 200 μm). F—Showing degeneration of some vasculature (arrows) with interstitial oedema (star; H&E scale bar, 200 μm).
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.09.0280
Kidney
Glomerular congestion and degeneration with proliferation of the mesangial cells within the glomeruli were seen. The tubular changes include degeneration and necrosis of the tubular epithelial cells, particularly in the proximal convoluted tubules. The presence of proteinaceous casts and cellular debris within the tubular lumen may be detected. Interstitial edema, hemorrhage, and infiltration of the renal interstitium by inflammatory cells, such as heterophils and mononuclear cells. There was congestion and dilation of the renal blood vessels (Figure 3).
Heart
Swollen and vacuolated myocardial fibers, indicating myocardial degeneration were detected. Congestion and dilation of the blood vessels within the myocardium and some vasculature suffer from degeneration (Figure 3).
Esophagus
Esophagitis was recorded and represented by; Hyperemia and congestion of the esophageal blood vessels, infiltration of the esophageal mucosa and submucosa by inflammatory cells, and epithelial cell necrosis and sloughing (Figure 4).
Photomicrograph of different organs. Esophagus (A) showing focal infiltration of inflammatory mononuclear cells (arrows) in the submucosa (H&E scale bar 200 μm). B—Desquamation of mucosal layer (arrows) (H&E scale bar 200 u m). Proventriculus (C) and (D) showing severe congestion of interventricular blood vessels (arrows) with the presence of desquamated epithelium and debris in lumen (star) (H&E scale bar 200 μm). Intestine (E) showing enteritis in which thinning and desquamation of villi (black arrows), infiltration of submucosa with mononuclear inflammatory cells (blue arrow) and dilated blood vessels with inflammatory cells (green arrow) (H&E scale bar 200 μm). F—Showing loss of villi lining epithelium (arrows) and infiltration of submucosa with mononuclear inflammatory cells (stars) (H&E scale bar 200 μm).
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.09.0280
Proventriculus
Thickening of the proventricular wall due to edema, hemorrhage, and severely dilated blood vessels was seen. Inflammation and necrosis of the proventricular mucosa so, desquamation of epithelial cells and debris into lumen (Figure 4).
Intestine
The intestine exhibited a profound inflammatory response, characterized by a massive influx of heterophils and mononuclear cells into the mucosa and submucosa. The intestinal blood vessels were dilated and congested, while the intestinal villi showed signs of desquamation and sloughing, leading to an accumulation of feed material, debris, bacterial colonies, and desquamated cells in the lumen. Additionally, oedema and haemorrhage were observed within the intestinal wall (Figure 4).
Trachea
Infiltration of the tracheal mucosa by mononuclear inflammatory cells. Also, necrosis and sloughing of the tracheal epithelium lead to the presence of exudate or mucus within the tracheal lumen (Figure 5).
Photomicrograph of different organs; Trachea (A) showing severe desquamation and loss of mucosa (arrows) (H&E scale bar 200 μm). B—Focal infiltration of mucosa with mononuclear inflammatory cells (arrow) (H&E scale bar 200 μm). Lungs (C) showing diffuse infiltration of interstitial alveoli by inflammatory cells (stars) leading to atelectasis of alveoli (black arrows). The bronchioles were packed with inflammatory cells and RBCs (green arrows) (H&E scale bar 200 μm). D—Showing diffuse infiltration of interstitial alveoli by inflammatory cells (stars). Focal area of suppurative inflammation (arrow) (H&E scale bar 200 μm).
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.09.0280
Lungs
Pneumonia was present in most cases in which, congestion of the pulmonary blood vessels and thickening of the alveolar septa due to edema and inflammation. Heavy infiltration of the alveolar and interstitial spaces by inflammatory cells. Accumulation of exudate, cellular debris, and fibrin within the alveolar spaces may be seen. In some cases, focal areas of necrosis and suppurative inflammation within the lung parenchyma may be detected.
Discussion
The ostrich industry is a burgeoning behemoth in the global poultry market, with an estimated annual production of over 1.5 million tons of meat and 1.2 million tons of eggs.14 In Egypt, ostrich farming is a rapidly expanding sector, with numerous farms sprouting up to meet the increasing demand for ostrich products. However, the occurrence of virulent microorganisms, such as E coli, poses a substantial risk to human health and the industry’s sustainability. Avian pathogenic E coli is a highly virulent strain that causes severe disease and mortality in birds, leading to significant economic losses for farmers.15
APEC is a ticking time bomb for the poultry industry, as APEC infections can unleash a deadly storm in chicks, triggering acute and subacute septicemia that can be fatal. The infection can spread like wildfire, claiming lives through acute septicemia in the yolk sac and respiratory system. If it progresses to subacute septicemia, it can unleash a trio of devastating consequences: pericarditis, perihepatitis, and airsacculitis, leaving chicks on the brink of disaster as seen in our study; the morbidity rate was 36% and the mortality rate was 7.6%. The first week of a chick’s life is a make-or-break period, and a mortality rate above 1% is a warning sign that the entire production system is on the verge of collapse. Industry giants like Aviagen and the European Union sound the alarm, stressing the need to keep first-week mortality rates below 0.7% to safeguard the welfare of birds and the future of the industry.16 Escherichia coli emerges as a leading perpetrator, responsible for a significant proportion of mortalities. A closer look at the evidence reveals a startling truth: a staggering 70% of chicks that succumb to death within a critical 48- to 72-hour window after hatching exhibit the telltale signs of colibacillosis, a devastating consequence of E coli infection.17
Over 1,000 E coli serotypes have been identified, yet only a limited subset has been linked to avian diseases. The primary reservoir of E coli is the intestinal tract of poultry, where it is present in high concentrations, with approximately 106 CFU/g of feces in chickens. Additionally, E coli has been frequently isolated from the upper respiratory tract, skin, and feathers of birds, comprising both pathogenic and non-pathogenic strains.18
Numerous E coli serotypes have been identified in various studies, including O103, O106, O27, O78, O164, O158, and O44.18–20 Specifically, serotype O27 has been isolated from 3-day-old layer chickens exhibiting symptoms of enlarged belly, watery diarrhea, and omphalitis.21 Furthermore, Konemann et al21 demonstrated that E coli strains under serogroups O78, O103, and O128 caused disease manifestations 24 h earlier when administered via the intraperitoneal route compared to the oral route. The infected birds displayed respiratory distress, congestion, hemorrhages, and mild pericardial fluid increase, with lungs showing congestion, pulmonary edema, airsacculitis, and myocarditis. Notably, Ellakany et al18 found that strains O78, O112, and O148 were more pathogenic, particularly when administered via the intraperitoneal route. Consistent with these findings, our study also isolated the same serotypes, including O78 and O103, highlighting the significance of these serotypes in avian colibacillosis.
The detection of the O78 serogroup of our study samples is a concerning finding, given its zoonotic potential and association with various human diseases, including invasive infections, neonatal meningitis, and sepsis. Notably, the CDC have identified 6 non-O157 STEC strains (O26, O45, O103, O111, O145, and O121) as responsible for approximately 70% of non-O157 STEC-related outbreak-associated diseases.22 Our study revealed the presence of one serotype from this “Big Six” group, specifically O103, which underscores the potential public health implications of these findings.
Previous studies20 have reported the occurrence of untypeable E coli isolates, which is credited to the limited number of monospecific antisera used for characterization. Currently, approximately 180 O antigens are employed to categorize E coli strains into O serogroups. In this study, 30 antisera were utilized in 2 laboratories, which may not be sufficient to identify all strains. Even when all 181 antisera are applied, some isolates remain untyped. The reasons for failed typing include the occurrence of surface antigens, such as the K antigen, which can inhibit O antigen agglutination, as well as the existence of rough strains that autoagglutinate and potentially novel serotypes that have not yet been identified.19 Consistent with these findings, our study revealed that approximately 8% of the isolates remained untypeable, highlighting the complexity of E coli serotyping and the need for further characterization methods.
In terms of Enterobacteriaceae, the coexistence of APEC E coli, Salmonella, Clostridium, and Enterobacteriaceae in ostriches poses a significant threat to human health, as these bacteria can contaminate meat and eggs, leading to foodborne illnesses.23 APEC E coli, with its ability to resist multiple antibiotics, and Salmonella, with its notorious serotypes such as Salmonella Enteritidis and Salmonella typhimurium, can synergistically increase the risk of foodborne illnesses in humans.24 The presence of these microorganisms in ostriches highlights the need for effective control measures to ensure the safety of ostrich meat and eggs for human consumption. Furthermore, the potential for horizontal gene transfer between these pathogens could lead to the development of even more virulent and antibiotic-resistant strains, exacerbating the public health concern.24 Therefore, it is essential to implement integrated strategies for the control and prevention of APEC E coli, Salmonella, Clostridium, and Enterobacteriaceae in ostriches, including vaccination, biosecurity measures, and antimicrobial stewardship, to mitigate the risk of foodborne illnesses and protect human health.15,26
The gross and microscopic findings of this study provide compelling evidence of the severe pathological changes associated with E coli infection in ostriches. The high incidence of E coli in various tissues suggests a systemic infection that can lead to multiorgan failure.27 The presence of pneumonia, characterized by congestion, edema, and consolidation of the lungs, is a significant finding, as it can lead to respiratory distress and mortality. This is consistent with the findings of. Yehia et al28 described that E coli was the most common bacterial isolate from the lungs of poultry with respiratory disease.
A study conducted in Brazil analyzed 225 E coli isolates from broiler turkeys suffering from air sac inflammation. The researchers found that 67% of the isolates had the iucD gene, which is linked to iron uptake. Additionally, they found the presence of the papC gene and the astA gene in some of the isolates. These findings suggest that a significant proportion of E coli strains associated with air sac inflammation in broiler turkeys may possess certain genetic traits that could contribute to their pathogenicity.29
Unraveling the mysterious path of APEC infection as the research suggests that APEC may infiltrate the body by traversing nonphagocytic cells, such as those lining the trachea or fibroblasts, in a process known as transcellular dissemination. The air sacs and lungs are thought to be the primary entry points for APEC to gain access to the bloodstream, but the exact mechanisms by which avian factors facilitate this process remain unclear and may differ depending on the specific APEC serotype.30
The identification of virulence-associated genes in the E coli isolates is a significant finding, as it suggests that these strains may be more virulent and capable of causing severe disease. The multiplex PCR results show that the E coli O27 isolate had 6 virulence-related genes, which is a higher number of virulence genes compared to the other isolates. This is consistent with the findings of Wilczyński et al,31 who reported that E coli isolates with multiple virulence genes were more likely to cause severe disease in poultry.
The classification of E coli as an APEC strain is genetically defined by the occurrence of at least five out of eight specific virulence factors. The pathogenicity of APEC strains is enabled by various virulence factors, including adhesins (tsh and papA), protectins (iss), toxins (astA, vat, cvi, and cva), and iron acquisition systems (irp2 and iucD). These genes are typically situated on mobile genetic elements, such as plasmids, transposons, pathogenicity islands, and bacteriophages, which can occur individually or in combinations, enabling the bacterium to acquire and express these virulence factors.
The occurrence of the irp2 and iucD genes in some isolates matched the outcomes of Wang et al,32 who reported that these genes were commonly associated with APEC E coli. The documentation of these virulence genes in the E coli O27 isolates suggests that this strain may be more powerful and capable of causing severe disease in ostriches. This is supported by the fact that the E coli O27 isolate was isolated from a bird with severe clinical symptoms of colibacillosis and respiratory disease as appeared in the demonstrated clinical signs.
In recent years, a team of researchers has been on a mission to crack the code of APEC’s sinister pathogenesis and epidemiology. They’ve been hunting for the secret markers that can distinguish between harmless microbes and the deadly pathogens that wreak havoc on our bodies.33 Abu El-Hammed et al34 uncovered a hidden gem among E coli O27 serotype isolates - one special isolate with a potent arsenal of 6 virulence genes, including the notorious “astA, iss, papC, iucD, vat, and cva/cvi”. Our finding echoes similar research in Nepal by Subedi et al35 which revealed APEC-associated virulence genes in broiler chickens. Meanwhile, Kwon et al12 had previously stumbled upon a similar quartet of virulence genes (iss, vat, iucD, and cvi/cva) in a group of 18 avian E coli strains. It seems that these genes are more common than we thought, and their presence could be a harbinger of trouble in the avian world.
The E coli isolates in this research resulting from organs exhibiting overt pathological lesions displayed phenotypic and genotypic traits indicative of a robust correlation with the clinical manifestations of colibacillosis. Furthermore, a positive association was detected between the severity of colibacillosis and respiratory disease, and the number of genes present in the isolated strains, implying a potential causal relationship.31
A study in Japan compared E coli isolates from hens with colibacillosis (a disease) to those from healthy hens. The results exhibited that the iss gene was more common among isolates from sick birds, indicating a potential link to the disease. The papC gene, conversely, was found in only 24% of isolates from birds with colibacillosis and was absent in isolates from healthy birds.36 The decision to sequence the genes from the E coli O27 isolate was based on its high virulence potential, as indicated by the occurrence of multiple virulence genes. Sequencing the genes from this isolate will provide valuable data on the genetic properties of APEC E coli in ostriches.
In comparison to other studies, the findings of this study are consistent with reports of E coli infection in birds but also highlight the complexity and severity of the disease in ostriches. In contrast, Osman et al37 recognized that the O27 strain of E coli, when administered to 21-day-old chicks, is not a pathogenic bacterium. Instead, it has positive effects on growth performance and immune system development, similar to those seen with probiotics. Based on these findings, the authors suggest that this strain could be a suitable candidate for use as a probiotic. The documentation of multiple E coli serotypes and virulence genes of E coli O27 has significant implications for the development of effective vaccines and diagnostic tools for the control and prevention of E coli infection in ostriches.
In conclusion, This research offers new insights into the pathology and microbiology of E coli infection in ostriches. The findings align with earlier reports of E coli infections in birds, highlighting the complexity and severity of the disease in ostriches. Additionally, the presence of E coli poses significant risks related to foodborne illnesses, particularly through the consumption of ostrich meat. These concerns emphasize the need for thorough monitoring and control measures in ostrich farming. Further investigations are required to understand the epidemiology and control of avian pathogenic E coli in ostriches, particularly in Egypt, to ensure the sustainability of the ostrich industry and protect human health.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org.
Acknowledgments
The authors express their sincere appreciation to the Researchers Supporting Project No. RSPD2024R986 at King Saud University in Riyadh, Saudi Arabia.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.
Funding
The authors have nothing to disclose.
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