[Weiboxin] Epidemiology, Clinical Manifestations, PCR-Based Differential Diagnosis, and Prevention and Control of Haemophilus paragallinarum in Chickens

This disease can occur worldwide and infect chickens of any age, with the highest susceptibility observed in birds aged 4 weeks to 3 years. However, individual variability exists; older chickens, in particular, tend to exhibit more severe clinical signs, and the course of the disease may be prolonged. The primary sources of infection are sick chickens and carrier chickens, with chronically ill birds and subclinically infected carriers being the main drivers of outbreaks within flocks. The disease is transmitted via the respiratory tract through droplets and dust, but in most cases it is contracted through the gastrointestinal tract by ingesting contaminated drinking water and feed. The disease primarily occurs during winter and early spring and spreads relatively rapidly.

The disease has a short incubation period, and in naturally infected chickens, clinical signs typically develop within 1 to 3 days.

In the early stages of the disease, inflammation primarily affects the nasal cavity and paranasal sinuses, initially presenting as a thin nasal discharge that later becomes serous. Coughing may also occur. Subsequently, edema develops around the eyes, accompanied by conjunctival inflammation, anorexia, reduced water intake, and weight loss. As the inflammation spreads to the lower respiratory tract, dyspnea ensues, often with rales. If the condition becomes chronic or is complicated by secondary infections, the flock may emit a foul odor, and affected birds will frequently shake their heads or use their feet to scratch the beak in an attempt to dislodge foreign material from the respiratory tract. In the absence of complications, the mortality rate associated with this disease is relatively low.

Postmortem examination revealed acute catarrhal inflammation of the nasal cavity and sinus mucosa in the dead chickens, accompanied by congestion and edema; the mucosal surfaces were heavily coated with mucus, and the sinus cavities contained copious curd-like exudate. Catarrhal conjunctivitis was also observed, with marked subcutaneous edema of the wattles; in severe cases, the laryngeal and tracheal mucosa became hyperemic and adhered to thick, viscous mucus. In laying hens, the oviducts contained caseous yellow exudate, the yolk sacs were atrophied, and the ovarian follicles exhibited congestion, degeneration, and hemorrhage, whereas no obvious lesions were found in other internal organs. If secondary infections occur, pathological changes characteristic of the corresponding diseases will develop.

Infectious laryngotracheitis in chickens. Similarities between the two All of them are contagious, and affected chickens exhibit nasal discharge and conjunctivitis. Difference This disease is caused by the infectious laryngotracheitis virus in chickens; however, it can also infect pheasants, turkeys, and quails. Affected chickens exhibit coughing, adventitious lung sounds during respiration, extension of the head and neck during inspiration accompanied by wheezing and vocalization, and in severe cases, spasmodic coughing with hemoptysis. The feathers, bedding, and walls are often contaminated as a result. Postmortem examination reveals necrosis and hemorrhage of the larynx and trachea, with blood or thrombi present and covered by caseous, yellowish-white fibrinous pseudomembranes. 
 

Klebsiella infection in chickens. Similarities between the two All cases are contagious. Affected chickens exhibit depression, head drooping and neck retraction, tearing, swollen eyelids, conjunctivitis, swelling of the infraorbital sinus, and unilateral or bilateral facial swelling. Necropsy reveals no obvious gross lesions in any internal organs. Difference This disease is caused by Klebsiella infection; in severe cases, swelling may also occur in the head and neck, with caseous material present in the infraorbital sinus, typically about the size of a soybean, and even the eyeball may become swollen. The cornea is prone to rupture, yet there is no serous nasal discharge, nor do affected animals sneeze or shake their heads.

Chicken swollen-head syndrome. Similarities between the two All of these conditions are contagious. Affected chickens often exhibit head-shaking and sneezing, with conjunctival swelling and congestion, as well as swelling of the eyelids and face. The comb and lower jaw may also show edema, leading to a reduction in egg production. Difference This disease is caused by infection with the infectious bronchitis virus. In affected chickens, the lacrimal glands become swollen, and swelling of the head typically begins 12 to 24 hours after onset, usually starting around the eyes; in the early stages, the birds will frequently use their claws to scratch their faces. Broiler breeders may also exhibit depression, persistent stupor, repeated head shaking, torticollis, opisthotonus—resembling a posture of looking up at the stars. Postmortem examination reveals mild congestion of the nasal turbinate mucosa and yellowish edema of the subcutaneous tissue, which subsequently progresses to suppuration. 
 

1. Nucleic acid testing: Detection of the pathogen using PCR technology. chicken The DNA of Haemophilus species can be detected using this method, which exhibits high sensitivity and specificity.

Weiboxin Biotechnology provides the corresponding assay kits:

2. Vaccination. Flocks can enhance their disease resistance and prevent illness through direct vaccination with bacterial vaccines. In China, bivalent oil-emulsion vaccines against Haemophilus paragallinarum serotypes A and C are commonly used; alternatively, trivalent ABC nasal vaccine may also be selected. The first vaccination is administered at 40 days of age, with a 0.3 mL intramuscular injection per bird; a second booster dose, using the same volume, is given around 120 days of age. In addition, laying hens should receive a 0.5 mL injection prior to the onset of egg production, which helps ensure they remain free from infection throughout the entire laying period. 
 

3. Strengthen feeding management. It is best for poultry farms to practice on-farm breeding and rearing, minimizing the introduction of breeding stock from outside the region. If external sourcing is necessary, such introductions must be strictly prohibited from flocks that have previously experienced the disease. Farms should adopt a “all-in, all-out” management system: from the start of the rearing cycle through to market withdrawal, no new birds are to be added midway; the entire flock must be sold off, followed by thorough disinfection of the poultry houses. All removed manure and other foreign materials must be collected and transported to a centralized site for disinfection and anaerobic fermentation, after which the houses must remain empty for several days before a new flock can be introduced. 
 

4. Pharmacotherapy. In adult chickens, administer 100–200 mg of streptomycin per bird per injection; for mild cases, give a single dose, and for severe cases, administer 2–3 consecutive doses. In the event of an outbreak affecting a flock, aerosol treatment with streptomycin is effective. Concurrently with streptomycin therapy, symptomatic treatment should also be implemented: for conjunctivitis or rhinitis, irrigate the eyes and nasal passages with 2% boric acid solution, followed by instillation of penicillin eye drops for enhanced efficacy; if curd-like, coagulated material is present in the sinus cavities, surgical intervention may be necessary to incise and remove it using forceps. 
 

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Guangzhou Weiboxin Biotechnology Co., Ltd. is located in the national-level innovation park—Guangzhou Science City—and is a provincial-level “Little Giant” high-tech enterprise specializing in the forward R&D, manufacturing, sales, and technical services of diagnostic reagents for animal epidemics. The company is also recognized as a “Contract-Honoring and Credit-Keeping Enterprise” in Guangdong Province and a provincial demonstration unit for intellectual property, as well as a industry–university–research collaboration base of Guangdong Food and Drug Vocational College and an executive director unit of the Veterinary Diagnostic and Biological Products Committee of the Guangdong Society of Animal Husbandry and Veterinary Medicine. It has been designated by multiple research institutes, including the Entrepreneurship College of Jinan University in Guangdong Province, as an innovative enterprise with strong growth potential. Furthermore, it has been rated as a “Specialized, Refined, Distinctive, and Innovative” enterprise at both the municipal and provincial levels, receiving awards such as “Most Investment-Valuable Enterprise” and “Annual African Swine Fever and Pig Disease Testing Service Provider.” The company has also obtained approval numbers from the Ministry of Agriculture and Rural Affairs for its veterinary drug products: Veterinary Drug Registration No. 191438923 (African Swine Fever Virus Fluorescent PCR Diagnostic Kit), Veterinary Drug Registration No. 191438213 (Reproductive and Respiratory Syndrome Virus ELISA Antibody Detection Kit), and Veterinary Drug Registration No. 191438875 (Classical Swine Fever Virus Blocking ELISA Antibody Detection Kit). In the 11th China Innovation and Entrepreneurship Competition, the company won the Excellence Award in the Growth Category of the Biopharmaceutical Industry; in the Nanotechnology Industry Technology Competition under the same event, it secured the Provincial Second Prize in the Growth Category; and in the National Finals of the Nanotechnology Industry Technology Innovation Special Competition within the China Innovation and Entrepreneurship Competition, it was awarded the National Third Prize in the Growth Category. The company has consecutively received the A-level Tax Credit Honor Certificate, the Four-Star Trademark Brand Certification, and the Two-Integration Management System Assessment Certificate each year, while also holding ISO 9001 International Quality Management System Certification, ISO 14001 International Environmental Management System Certification, and GMP Certification from the Ministry of Agriculture. Since its establishment, the company has been granted a total of 24 patents, including 5 invention patents, 15 utility model patents, and 4 design patents, in addition to more than ten registered trademarks.

The company boasts robust technical capabilities and a team of world-class professionals, including dozens of masters, doctors, and returnees who studied abroad, as well as numerous senior-title technical experts. Currently, the company’s primary focus is on the research and development of molecular diagnostic reagents. Its core R&D team has developed more than 600 products spanning molecular diagnostics and immunoassays, including public-health–oriented fluorescent PCR test kits, animal disease–control–oriented fluorescent PCR test kits, clinical and research–grade fluorescent quantitative PCR kits, and transgenic–identification test kits (ZL2006). The company has also established a nationwide distribution network covering more than ten major cities, such as Beijing, Shanghai, Hangzhou, Nanjing, Xi’an, Chongqing, Lanzhou, Zhengzhou, and Qingdao.

Looking ahead, Weiboxin will remain steadfast in its commitment to continuously enhance product quality and service standards. Leveraging a rapid and efficient research platform and abundant biomedical resources, we will conduct extensive and in-depth R&D and scientific research in the biomedical field, thereby contributing to human health and advancing life sciences. Quality is our lifeline, and innovation is our soul; we will unwaveringly uphold this philosophy as we strive to become the premier supplier of rapid diagnostic reagents and instruments.