What is Dr. Zubair Khalid's research focus?

Dr. Zubair Khalid specializes in molecular virology, mRNA vaccine development, and computational biology, with a focus on avian pathogens like IBDV and Avian Reovirus.

Where is Dr. Zubair Khalid currently working?

Dr. Zubair Khalid is a Postdoctoral Research Associate at the University of Maryland (UMD), specifically within the Department of Animal and Avian Sciences.

Duck Diseases: A Comprehensive Guide to Common Health Issues in Waterfowl

Introduction

Domestic ducks (Anas platyrhynchos domesticus and Cairina moschata) are economically important poultry species raised for meat, eggs, and feathers. They are susceptible to a wide spectrum of infectious and non-infectious diseases. The phrase "what is ducks disease" commonly refers to any of several acute or chronic conditions affecting waterfowl, including bacterial septicemias, viral enteritides, and parasitic infestations [1]. This guide provides a systematic review of the major disease categories, with a focus on bacterial pathogens, their pathogenesis, diagnostic modalities, and control measures. Dense population management and environmental stressors predispose flocks to outbreaks, and the emergence of antimicrobial resistance (AMR) further complicates therapy [2, 3].

Etiology and Major Pathogens

Duck diseases arise from diverse etiological agents: bacteria, viruses, parasites, and environmental toxins. Among bacteria, Riemerella anatipestifer (RA), Pasteurella multocida, Escherichia coli, Salmonella enterica serovars, and Campylobacter spp. are most frequently reported [4, 5, 2]. Viral pathogens include duck plague virus (DPV) [6, 7, 8, 9, 10, 11, 12], duck hepatitis A virus (DHAV) [13, 14, 15], duck Tembusu virus (DTMUV) [16, 17], goose parvovirus (GPV) [18, 19], duck circovirus (DuCV) [18, 19, 20], duck astrovirus (DAstV) [21], duck orthoreovirus (DRV) [22], and adenoviruses [23]. Avian influenza virus (AIV) subtypes H5N6, H5Ny, and H3 are also significant [24, 25, 26, 27, 28]. Parasitic infections such as Eustrongylides tubifex cause proventricular pathology [29]. Non-infectious conditions include microplastic-induced neurotoxicity [30] and nutritional imbalances [31].

Table 1. Major Infectious Agents in Ducks

Epidemiology and Transmission

Epidemiological patterns vary by pathogen and production system. R. anatipestifer is transmitted horizontally via respiratory and cutaneous routes, with overcrowding and wet litter increasing transmission [4, 5]. Salmonella persists in the environment and is shed in feces, leading to horizontal and vertical transmission [2]. AIV cycles in wild waterfowl and can spill over into domestic flocks, with interannual seroprevalence differences observed in Arctic colonies [27]. DPV outbreaks occur in both vaccinated and unvaccinated flocks, indicating vaccine breakthroughs and the circulation of virulent strains [6, 12]. Co-infection with multiple agents, such as GPV, DuCV, and reovirus, is a major risk factor for syndromes like red skin and bristle feather syndrome [18]. Genomic surveillance reveals complex recombination dynamics in DuCV [20] and ongoing evolution of DHAV in Egypt [14] and China [13].

Clinical Signs and Pathology

Clinical presentations depend on the etiological agent and host age. Bacterial infections often manifest as acute septicemia with fibrinous polyserositis, pericarditis, and airsacculitis [4, 33]. R. anatipestifer causes ocular discharge, respiratory distress, ataxia, and high mortality in ducklings [4, 32]. Salmonella infection leads to diarrhea, dehydration, and sudden death [2]. Viral diseases show distinct pathology: DPV produces vascular lesions, hemorrhagic enteritis, and diphtheritic membranes in the esophagus and cloaca [6, 7, 12]. DHAV causes liver necrosis and hemorrhage, with mortality up to 95% in young ducklings [13, 14]. DTMUV induces ovarian regression and neurological signs [17]. GPV and DuCV are associated with poor feathering and growth retardation [18, 19]. Parasitic infection with E. tubifex provokes proventricular inflammation, as shown by transcriptomic analysis [29]. Non-infectious diseases like polyvinyl chloride microplastic exposure induce ferroptosis in the cerebral cortex, leading to neurological impairment [30].

Diagnostics

Accurate diagnosis requires a combination of clinical, pathological, laboratory, and molecular methods. For bacterial pathogens, isolation and identification remain the gold standard, but rapid molecular tests are increasingly employed. A versatile loop-mediated isothermal amplification (LAMP) assay with phenol red and lateral flow dipstick detection has been developed for R. anatipestifer [4]. Real-time recombinase polymerase amplification (RPA) targets virulent DPV strains [12]. CRISPR/Cas12a coupled with recombinase-aided amplification (RAA) provides sensitive detection of duck adenovirus 3 [23]. Quantitative LAMP assays exist for duck variant orthoreovirus [22]. Whole genome sequencing and evolutionary analyses are used for DHAV [14] and GPV/DuCV [19]. Serological tools include commercial ELISA kits for DTMUV [16] and hemagglutination inhibition for AIV [24]. Single-cell RNA sequencing and B cell receptor analysis can characterize immune responses to DHAV-1 vaccines [15].

Diagnostic Decision Workflow

flowchart TD
    A[Clinical signs: mortality, neurological, respiratory, diarrhea], > B{History & flock assessment}
    B, > C[Initial necropsy & gross pathology]
    C, > D[Sample collection: liver, spleen, brain, intestinal tract, swabs]
    D, > E[Bacteriology: culture on blood/MacConkey agar, Gram stain]
    D, > F[Virology: PCR, LAMP, RPA, sequencing]
    D, > G[Parasitology: direct microscopy, histopathology]
    E, > H[R. anatipestifer? Salmonella? E. coli?]
    F, > I[DPV? DHAV? AIV? DTMUV? GPV?]
    G, > J[Eustrongylides? coccidia?]
    H & I & J, > K[Differential diagnosis: rule out similar presentations]
    K, > L[Final etiological confirmation]
    L, > M[Antimicrobial sensitivity test (if bacterial)]
    M, > N[Treatment & control recommendations]

The workflow emphasizes the need for rapid point-of-care testing (e.g., LAMP) in field settings and advanced molecular characterization for surveillance [4, 23, 12].

Treatment

Therapeutic approaches depend on etiology. Bacterial infections require antimicrobial therapy guided by sensitivity testing due to rising AMR [2]. R. anatipestifer isolates show variable susceptibility; beta-lactams, tetracyclines, and fluoroquinolones have been used, but resistance is reported [5, 32]. The PorV protein of R. anatipestifer has been identified as a cross-protective antigen [32], and the OMP85 protein enhances virulence by recruiting complement regulators, representing a potential vaccine target [33]. For viral diseases, no specific antiviral treatments exist; supportive care and biosecurity are paramount. Vaccination is the mainstay of prevention: inactivated DTMUV vaccines induce cross-genotype immunity [16], while targeted mutagenesis of DPV ICP4 provides a DIVA vaccine [9]. Deletion of the N-terminal 400 amino acids of DPV pUL36 attenuates virulence and confers protection [7]. Curcumin has been proposed as a green antibiotic substitute to modulate gut health and reduce pathogen load [3].

Control and Prevention

Control strategies integrate biosecurity, vaccination, and management. Strict all-in/all-out practices, disinfection, and separation of age groups reduce pathogen introduction [1]. Vaccination programs should match circulating strains; for DPV, modified live and recombinant vaccines are available [6, 9]. DHAV resistance can be enhanced through host genetic factors, such as DNA methylation-mediated suppression of endocytosis [13]. For AIV, monitoring receptor-binding mutations is critical, as double mutations in hemagglutinin increase binding to human-type receptors [24]. Environmental management, including litter quality and ventilation, reduces stress and pathogen load. The use of artificial intelligence in precision veterinary medicine may improve early disease prediction [34]. Finally, one health surveillance of zoonotic agents like Bartonella henselae in ducks and insect vectors highlights cross-species risks [35].

Conclusion

Duck diseases encompass a broad range of infectious and non-infectious conditions that require integrated diagnostic and management approaches. Continued genomic surveillance, development of rapid field diagnostics, and judicious use of antimicrobials are essential to maintain flock health and mitigate zoonotic threats.

References

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[23] Zhang W, Tang Z, He S, et al. Detection of duck adenovirus 3 using RAA-CRISPR/Cas12a based lateral flow dipstick method. Front Microbiol. 2026. URL: https://pubmed.ncbi.nlm.nih.gov/42164672/

[24] Jin X, Han P, Wang Y, et al. Hemagglutinin double-mutation enhances binding of human-infecting avian influenza virus clade 2.3.4.4b H5Ny to human and SLe(X) receptors. EMBO Rep. 2026. URL: https://pubmed.ncbi.nlm.nih.gov/42303811/

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[29] Hao C, Bai Y, Xia S, et al. Transcriptomic Analysis of Domestic Ducks' Proventriculus Infected with Eustrongylides tubifex (Nitzsch 1819) Jägerskiöld 1909. Vet Sci. 2026. URL: https://pubmed.ncbi.nlm.nih.gov/42188957/

[30] Wang L, Song H, Wang T, et al. Preliminary evidence of polyvinyl chloride microplastics inducing ferroptosis in the cerebral cortex of ducks. Neurotoxicology. 2026. URL: https://pubmed.ncbi.nlm.nih.gov/42119735/

[31] Zhang WX, Tian G, Zhang KY, et al. Effects of oleic acid supplementation on ileal fatty acid digestibility, intestinal barrier function, and cecal microbiota in Pekin ducks fed a high-fat diet. Poult Sci. 2026. URL: https://pubmed.ncbi.nlm.nih.gov/42214187/

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[35] Santos LSD, Velho PENF, Oliveira J, et al. Between insects and birds: molecular evidence of Bartonella henselae DNA in Rhodnius prolixus (Stål, 1859) from an insectary and Cairina moschata (Linnaeus, 1758) ducks used as triatomine blood meal source. Rev Inst Med Trop Sao Paulo. 2026. URL: https://pubmed.ncbi.nlm.nih.gov/42307305/