Patho-epidemiological Study of Chronic Respiratory Disease (CRD) in Commercial Layer Chickens: A Case Report

Patho-epidemiological Study of Chronic Respiratory Disease (CRD) in Commercial Layer Chickens: A Case Report | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Patho-epidemiological Study of Chronic Respiratory Disease (CRD) in Commercial Layer Chickens: A Case Report Yahye Yasin Hassan, Ahmed Abdi mohomed, Mustafa Ibrahim Ali, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7991794/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Chronic Respiratory Disease (CRD), caused by Mycoplasma gallisepticum , is one of the most economically significant diseases of poultry worldwide. This case report describes the clinical, pathological, and epidemiological features of CRD in a commercial layer flock in Jigjiga, Somali Regional State, Ethiopia. A total of 5,100layer chickens reared under a deep litter system were affected. The outbreak resulted in 505 deaths, representing an overall mortality of 9.90%, and 1,417 clinically affected birds, giving a morbidity rate of 27.78%. Morbidity and mortality were higher in Block B (33.11% and 10.88%) than in Block A (25.11% and 9.41%), indicating increased susceptibility among older birds. Clinically, affected chickens exhibited respiratory distress, coughing, nasal discharge, and open-mouth breathing. Postmortem findings included catarrhal exudate in the trachea and bronchi, cloudy and foamy air sacs, and air sacculitis. Based on clinical signs and gross pathology, the condition was diagnosed as CRD. Treatment with Tylosin 20% (0.5 g/L of drinking water), coupled with improved ventilation, reduced overcrowding, and strict biosecurity, resulted in recovery of the flock. The study highlights the continued importance of CRD as a major health and economic threat in layer operations and underscores the need for routine monitoring, early diagnosis, and effective preventive measures. Veterinary Epidemiology Chronic Respiratory Disease Pathology Poultry Epidemiology Ethiopia Figures Figure 1 INTRODUCTION Chronic respiratory disease (CRD) is one of the most economically important diseases of chicken( 1 ). This disease is caused by Mycoplasma gallisepticum which are pleomorphic and lacks the ability of Gram staining, therefore the characterisation of mycoplasmas based on morphological characteristics is non-effective( 2 ). Mycoplasma gallisepticum infection spreads horizontally from bird to bird through direct contact, aerosols, and contaminated equipment, and it can also be transmitted vertically through infected eggs from hens to their offspring( 3 ). Gasping, respiratory rales, coughing, nasal discharge and rhinitis are the major signs of Chronic respiratory disease (CRD). Sometimes M. gallisepticum causes arthritis, salpingitis, conjunctivitis and fatal encephalopathy, In the commercial layer chickens, it causes marked decrease in eggs production and embryo mortality( 4 ). Diagnosis is made based on history, clinical signs and symptoms, post mortem findings ( 5 ). Therefore the objective of this case report is to show the clinical sign, postmortem examination and treatment approaches and the impact of those interventions towards chronic respiratory disease in a poultry farms. CASE HISTORY AND CLINICAL OBSERVATIONS A poultry farmer residing in Jigjiga, Somali Regional State, Ethiopia, reported a case of respiratory distress in a flock of commercial layer chickens, accompanied by the mortality of 505 birds within four days. According to the owner, the birds were reared under a deep litter system using sawdust as litter material. The farmer observed abnormal respiratory sounds, nasal discharge, sneezing, coughing, and open-mouth breathing among the affected birds. In addition, feed consumption had decreased, and the birds showed progressive weight loss. No medication had been administered prior to the onset of the disease. Clinical examination revealed dyspnea, rales, and open-mouth breathing. A marked drop in egg production was also reported, declining from 85% to approximately 60%. Post mortem examination of the dead birds showed the presence of inflammatory material (Catarrhal exudate) in trachea, bronchi, and Airsacculitis with cloudy and foamy air sacs (Fig. 1 ). TREATMENT Based on the flock history, clinical signs, and postmortem examination findings, the case was tentatively diagnosed as chronic respiratory disease (CRD). Treatment was initiated with Tylosin 20%, administered at a dosage rate of 0.5 g per liter of drinking water. The farmer was further advised to isolate the sick and suspected birds, ensure adequate ventilation, reduce dust levels within the poultry house, avoid overcrowding, and implement strict biosecurity measures in and around the farm premises. during a follow-up telephone conversation, the owner reported that the birds had become active, alert, and had returned to normal condition following treatment. RESULTS AND DISCUSSION Out of a total of 5,100 commercial layer chickens reared on a single farm consisting of two production houses (Block A and Block B), a total of 505 birds died, resulting in an overall mortality rate of 9.90%. The mortality was slightly higher in Block B (10.88%) compared to Block A (9.41%). The overall morbidity rate was 27.78%, with 33.12% in Block B and 25.12% in Block A, indicating a higher disease occurrence among the older flock (30 weeks) than in the younger one (17 weeks). The case fatality rate (CFR) ranged from 32.86% in Block B to 37.47% in Block A, with an overall mean of 35.64%, suggesting that once birds were clinically affected, a substantial proportion succumbed to the disease. Table 1 CRD under study along with morbidity, mortality patterns and age of the infection Farm block Total number of birds Age of birds (week) Number affected Number of Death Morbidity (%) Mortality (%) CFR (%) Block A 3400 17week 854 320 25.11 9.41 37.47 Block B 1700 30week 563 185 33. 11 10.88 32.85 Total 5100 1417 505 27.78 9.90 35.64 The present findings are in agreement with( 6 ). and ( 2 ). who reported CRD-associated mortalities ranging from 1% to 10%, but differ from the lower rates reported by ( 7 ). and( 8 ) (0.4%–2%). abnormal respiratory sounds, nasal discharge, sneezing, coughing, and open-mouth breathing among the affected birds similar clinal sign with ( 9 ). the presence of inflammatory material (Catarrhal exudate) in trachea, bronchi, and Airsacculitis with cloudy and foamy air sacs( 10 ). These results indicate that chronic respiratory disease (CRD) remains a major health and economic challenge in layer operations, leading to considerable mortality, high morbidity, and production losses. Implementation of strict biosecurity, and improved ventilation. Declarations Participant Consent Statement Informed consent was obtained from the legal guardian of the commercial poultry farm affected. The guardian agreed to the participation of the farm in this case report and consented to the publication of the clinical and pathological findings described in this preprint. All procedures and data collection were conducted in accordance with ethical standards, ensuring confidentiality and proper handling of all information. Availability of Data and Materials The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request. Conflict of Interest The authors declare that there are no conflicts of interest associated with this publication. Funding This study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Acknowledgments The authors sincerely thank the poultry farm owners and staff for their cooperation, hospitality, and assistance during the field investigation and data collection process References Karthik K, Bharathi R, Mahaprabhu R, Manimaran K, Shoba K (2018) Chronic respiratory disease outbreak in an organized native chicken farm Bayan R, Ujjan JA, Noureen A, Noman M, Malik MI, Rustam SA et al Seroprevalence of Mycoplasma gallisepticum amongst Commercial Layers in District Peshawar, Khyber Pakhtunkhwa Pakistan Ramadan N (2019) Mycoplasma gallisepticum overview in poultry. Am J Biomed Sci Res 4(5):354–355 Shoaib M (2019) Mycoplasmosis in poultry, a perpetual problem. J Microbiol Biotechnol Food Sci 8(6):1271 Singh LK, Devi KM (2020) Chronic respiratory disease in poultry: case report. Electronic file available at https://epashupalancom/4401/animal-disease/chronic-respiratory-disease-in-poultry-case-report/ Accessed on. ;27:23 Nunoya T, Kanai K, Yagihashi T, Hoshi S, Shibuya K, Tajima M (1997) Natural case of salpingitis apparently caused by Mycoplasma gallisepticum in chickens. Avian Pathol 26(2):391–398 Chary P, Padmavathi G, Sudhakar R, Reddy A, Rao P (1991) A study on mortality pattern in poultry Radi Z (1997) Avidin-biotin immunohistochemical detection of Mycoplasma gallisepticum antigens in turkey respiratory tissues with rabbit polyclonal primary antibodies Susitha Rajkumar SR, Reddy M, Somvanshi R (2017) Molecular detection and pathology of spontaneous cases of Chronic Respiratory Disease in chicken Vegad J (2007) A colour atlas of poultry diseases: an aid to farmers and poultry professionals. International Book Distributing Company Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7991794","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":537653754,"identity":"fde9bd02-c248-44f5-89c9-eec16746d7d4","order_by":0,"name":"Yahye Yasin 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07:12:41","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":30263,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7991794/v1/76ac73f0cfa29075eb6338ec.html"},{"id":94981352,"identity":"bc619efe-ee4f-4a2c-9a99-69aad1648fbc","added_by":"auto","created_at":"2025-11-03 05:36:19","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":339889,"visible":true,"origin":"","legend":"\u003cp\u003eA: Gasping, open-mouth breathing. B: Presence of inflammatory material (catarrhal exudate) in trachea. C: Airsacculitis with cloudy and foamy air sacs.\u003c/p\u003e","description":"","filename":"fourfacecopy.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7991794/v1/05d2535bd7cad849db2a401a.jpg"},{"id":94991018,"identity":"49a3ee35-3556-413f-954f-36f0d47f32e2","added_by":"auto","created_at":"2025-11-03 07:18:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":717057,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7991794/v1/7cf0ad35-72e1-4118-aaf3-ae3558e8ad27.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003ePatho-epidemiological Study of Chronic Respiratory Disease (CRD) in Commercial Layer Chickens: A Case Report\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eChronic respiratory disease (CRD) is one of the most economically important diseases of chicken(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). This disease is caused by Mycoplasma gallisepticum which are pleomorphic and lacks the ability of Gram staining, therefore the characterisation of mycoplasmas based on morphological characteristics is non-effective(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). \u003cem\u003eMycoplasma gallisepticum\u003c/em\u003e infection spreads horizontally from bird to bird through direct contact, aerosols, and contaminated equipment, and it can also be transmitted vertically through infected eggs from hens to their offspring(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eGasping, respiratory rales, coughing, nasal discharge and rhinitis are the major signs of Chronic respiratory disease (CRD). Sometimes M. gallisepticum causes arthritis, salpingitis, conjunctivitis and fatal encephalopathy, In the commercial layer chickens, it causes marked decrease in eggs production and embryo mortality(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Diagnosis is made based on history, clinical signs and symptoms, post mortem findings (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTherefore the objective of this case report is to show the clinical sign, postmortem examination and treatment approaches and the impact of those interventions towards chronic respiratory disease in a poultry farms.\u003c/p\u003e"},{"header":"CASE HISTORY AND CLINICAL OBSERVATIONS","content":"\u003cp\u003eA poultry farmer residing in Jigjiga, Somali Regional State, Ethiopia, reported a case of respiratory distress in a flock of commercial layer chickens, accompanied by the mortality of 505 birds within four days. According to the owner, the birds were reared under a deep litter system using sawdust as litter material. The farmer observed abnormal respiratory sounds, nasal discharge, sneezing, coughing, and open-mouth breathing among the affected birds. In addition, feed consumption had decreased, and the birds showed progressive weight loss. No medication had been administered prior to the onset of the disease. Clinical examination revealed dyspnea, rales, and open-mouth breathing. A marked drop in egg production was also reported, declining from 85% to approximately 60%. Post mortem examination of the dead birds showed the presence of inflammatory material (Catarrhal exudate) in trachea, bronchi, and Airsacculitis with cloudy and foamy air sacs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eTREATMENT\u003c/h2\u003e\u003cp\u003eBased on the flock history, clinical signs, and postmortem examination findings, the case was tentatively diagnosed as chronic respiratory disease (CRD). Treatment was initiated with Tylosin 20%, administered at a dosage rate of 0.5 g per liter of drinking water. The farmer was further advised to isolate the sick and suspected birds, ensure adequate ventilation, reduce dust levels within the poultry house, avoid overcrowding, and implement strict biosecurity measures in and around the farm premises. during a follow-up telephone conversation, the owner reported that the birds had become active, alert, and had returned to normal condition following treatment.\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS AND DISCUSSION","content":"\u003cp\u003eOut of a total of 5,100 commercial layer chickens reared on a single farm consisting of two production houses (Block A and Block B), a total of 505 birds died, resulting in an overall mortality rate of 9.90%. The mortality was slightly higher in Block B (10.88%) compared to Block A (9.41%). The overall morbidity rate was 27.78%, with 33.12% in Block B and 25.12% in Block A, indicating a higher disease occurrence among the older flock (30 weeks) than in the younger one (17 weeks). The case fatality rate (CFR) ranged from 32.86% in Block B to 37.47% in Block A, with an overall mean of 35.64%, suggesting that once birds were clinically affected, a substantial proportion succumbed to the disease.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCRD under study along with morbidity, mortality patterns and age of the infection\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFarm block\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal number of birds\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAge of birds (week)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNumber affected\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNumber of Death\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMorbidity (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMortality (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eCFR (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlock A\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3400\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e17week\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e854\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e320\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e25.11\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e9.41\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003e37.47\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eBlock B\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1700\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30week\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e563\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e185\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e33. 11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e10.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e32.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1417\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e505\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e27.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e9.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e35.64\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe present findings are in agreement with(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). and (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). who reported CRD-associated mortalities ranging from 1% to 10%, but differ from the lower rates reported by (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). and(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e) (0.4%\u0026ndash;2%). abnormal respiratory sounds, nasal discharge, sneezing, coughing, and open-mouth breathing among the affected birds similar clinal sign with (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). the presence of inflammatory material (Catarrhal exudate) in trachea, bronchi, and Airsacculitis with cloudy and foamy air sacs(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). These results indicate that chronic respiratory disease (CRD) remains a major health and economic challenge in layer operations, leading to considerable mortality, high morbidity, and production losses. Implementation of strict biosecurity, and improved ventilation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eParticipant Consent Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from the legal guardian of the commercial poultry farm affected. The guardian agreed to the participation of the farm in this case report and consented to the publication of the clinical and pathological findings described in this preprint. All procedures and data collection were conducted in accordance with ethical standards, ensuring confidentiality and proper handling of all information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no conflicts of interest associated with this publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors sincerely thank the poultry farm owners and staff for their cooperation, hospitality, and assistance during the field investigation and data collection process\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKarthik K, Bharathi R, Mahaprabhu R, Manimaran K, Shoba K (2018) Chronic respiratory disease outbreak in an organized native chicken farm\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBayan R, Ujjan JA, Noureen A, Noman M, Malik MI, Rustam SA et al Seroprevalence of Mycoplasma gallisepticum amongst Commercial Layers in District Peshawar, Khyber Pakhtunkhwa Pakistan\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRamadan N (2019) Mycoplasma gallisepticum overview in poultry. Am J Biomed Sci Res 4(5):354\u0026ndash;355\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShoaib M (2019) Mycoplasmosis in poultry, a perpetual problem. J Microbiol Biotechnol Food Sci 8(6):1271\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSingh LK, Devi KM (2020) Chronic respiratory disease in poultry: case report. Electronic file available at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://epashupalancom/4401/animal-disease/chronic-respiratory-disease-in-poultry-case-report/\u003c/span\u003e\u003cspan address=\"https://epashupalancom/4401/animal-disease/chronic-respiratory-disease-in-poultry-case-report/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e Accessed on. ;27:23\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNunoya T, Kanai K, Yagihashi T, Hoshi S, Shibuya K, Tajima M (1997) Natural case of salpingitis apparently caused by Mycoplasma gallisepticum in chickens. Avian Pathol 26(2):391\u0026ndash;398\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChary P, Padmavathi G, Sudhakar R, Reddy A, Rao P (1991) A study on mortality pattern in poultry\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRadi Z (1997) Avidin-biotin immunohistochemical detection of Mycoplasma gallisepticum antigens in turkey respiratory tissues with rabbit polyclonal primary antibodies\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSusitha Rajkumar SR, Reddy M, Somvanshi R (2017) Molecular detection and pathology of spontaneous cases of Chronic Respiratory Disease in chicken\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVegad J (2007) A colour atlas of poultry diseases: an aid to farmers and poultry professionals. International Book Distributing Company\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Jigjiga University","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Chronic Respiratory Disease, Pathology, Poultry, Epidemiology, Ethiopia","lastPublishedDoi":"10.21203/rs.3.rs-7991794/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7991794/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eChronic Respiratory Disease (CRD), caused by \u003cem\u003eMycoplasma gallisepticum\u003c/em\u003e, is one of the most economically significant diseases of poultry worldwide. This case report describes the clinical, pathological, and epidemiological features of CRD in a commercial layer flock in Jigjiga, Somali Regional State, Ethiopia. A total of 5,100layer chickens reared under a deep litter system were affected. The outbreak resulted in 505 deaths, representing an overall mortality of 9.90%, and 1,417 clinically affected birds, giving a morbidity rate of 27.78%. Morbidity and mortality were higher in Block B (33.11% and 10.88%) than in Block A (25.11% and 9.41%), indicating increased susceptibility among older birds. Clinically, affected chickens exhibited respiratory distress, coughing, nasal discharge, and open-mouth breathing. Postmortem findings included catarrhal exudate in the trachea and bronchi, cloudy and foamy air sacs, and air sacculitis. Based on clinical signs and gross pathology, the condition was diagnosed as CRD. Treatment with Tylosin 20% (0.5 g/L of drinking water), coupled with improved ventilation, reduced overcrowding, and strict biosecurity, resulted in recovery of the flock. The study highlights the continued importance of CRD as a major health and economic threat in layer operations and underscores the need for routine monitoring, early diagnosis, and effective preventive measures.\u003c/p\u003e","manuscriptTitle":"Patho-epidemiological Study of Chronic Respiratory Disease (CRD) in Commercial Layer Chickens: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-03 05:36:14","doi":"10.21203/rs.3.rs-7991794/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1076d524-4a84-4fb5-983a-ee05cc739a8e","owner":[],"postedDate":"November 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57309847,"name":"Veterinary Epidemiology"}],"tags":[],"updatedAt":"2025-11-03T05:36:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-03 05:36:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7991794","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7991794","identity":"rs-7991794","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}