Clinical Recognition and Pathological Findings in Sheep and Goat Pox

Early recognition of sheep and goat pox (SGP) is critical for limiting disease spread and initiating timely control measures. As one of the most contagious viral diseases affecting small ruminants, SGP can rapidly involve a large proportion of susceptible animals within a flock. While laboratory confirmation remains essential, the ability to identify characteristic clinical and pathological changes in the field allows veterinarians to make informed decisions regarding isolation, sample collection, and outbreak management. Familiarity with the disease progression also helps differentiate SGP from other conditions presenting with skin lesions. 

Recognizing the Clinical Course 

Following exposure, the virus multiplies within the host tissues before clinical signs become evident. The incubation period generally ranges from 4–8 days in sheep pox and 4–15 days in goat pox and lumpy skin disease. During the initial stage of infection, affected animals commonly develop fever, increased respiratory rate, swollen eyelids, and nasal discharge. The virus subsequently spreads through the bloodstream, initially localizing in the lymph nodes before disseminating to organs such as the liver, lungs, and spleen^1,2.

As the disease progresses, animals often exhibit reduced appetite and a characteristic hunched posture. Within approximately 48 hours of systemic illness, small, round skin lesions measuring about 1 cm begin to appear. These lesions are most commonly observed on the head, neck, ears, axillary region, and beneath the tail. Ocular and nasal inflammation frequently accompany the skin lesions, along with enlargement of superficial lymph nodes, particularly those around the shoulder region. Excessive salivation may also be present in some affected animals. 

Gross Pathological Findings¹ 

Postmortem examination provides several characteristic findings that can strengthen clinical suspicion of SGP. The tracheal mucosa often appears congested, while multiple lentil- or bullet-like nodules may be present. White necrotic patches are commonly observed within the lungs and spleen, and affected lymph nodes frequently show grayish necrotic lesions. 

Another notable finding is the accumulation of blood-tinged fluid within the pleural cavity. In some animals, the lungs exhibit multiple consolidated areas, reflecting viral pneumonia or secondary bacterial involvement. These pathological changes provide valuable clues when evaluating animals that succumb during an outbreak. 

Histopathological Features 

Microscopic examination reveals extensive changes involving both the epidermis and dermis. Common findings include hyperkeratosis, acanthosis, excessive keratin production, intercellular and intracellular edema, and degenerative changes affecting sebaceous glands and hair follicles^3,4. 

Pulmonary tissue may demonstrate congestion, red hepatization, exudation, coagulative necrosis, and a marked inflammatory response. Thickening of the interlobular septa is also observed. Lymphoid tissues frequently show depletion of lymphocytes within the paracortical regions, while germinal centers may be absent in both the spleen and lymph nodes². These pathological findings correlate well with the systemic nature of capripoxvirus infection. 

Practical Clinical Insights 

During field investigations, veterinarians should evaluate the entire clinical picture rather than relying on a single lesion. The combination of fever, generalized nodular skin lesions, enlarged lymph nodes, respiratory involvement, and characteristic postmortem changes substantially increases clinical suspicion for SGP. 

Particular attention should be paid to: 

• Distribution of nodular lesions on the head, neck, ears, axillae, and tail region. 

• Early systemic signs preceding skin lesion development. 

• Presence of enlarged superficial lymph nodes. 

• Evidence of pneumonia or pleural fluid in animals that die during an outbreak. 

• Typical necrotic lesions in lungs, spleen, and lymph nodes during postmortem examination. 

Because sheep pox and goat pox produce very similar clinical and pathological manifestations, field findings alone cannot reliably distinguish between the two infections. Nevertheless, prompt recognition of these characteristic features enables timely sample collection, laboratory confirmation, and implementation of appropriate disease control measures, ultimately supporting more effective outbreak management in small ruminant populations. 

References 

1. Hamdi J, Bamouh Z, Jazouli M, Alhyane M, Safini N, Tadlaoui KO, Fihri OF, El Harrak M. Experimental infection of indigenous North African goats with goatpox virus. Acta Veterinaria Scandinavica. 2021;63:1. https://link.springer.com/content/pdf/10.1186/s13028-021-00574-2.pdf 

2. Jadhav S, Veeregowda BM, Tadakod S, Naragund M, GB MR. Sheep and Goat Pox Disease: Epidemiology, Diagnosis, Prevention and Control. InAdvances in Animal Sciences (Volume 1) 2025 Jul 26 (pp. 35-47). Cornous Publications LLP. https://www.researchgate.net/profile/Sunil_Tadakod/publication/394089319 

3. Zewdie G, Derese G, Getachew B, Belay H, Akalu M. Review of sheep and goat pox disease: current updates on epidemiology, diagnosis, prevention and control measures in Ethiopia. Animal diseases. 2021 Nov 15;1(1):28. https://link.springer.com/content/pdf/10.1186/s44149-021-00028-2.pdf 

4. Manjunathareddy GB, Saminathan M, Sanjeevakumar L, Rao S, Dinesh M, Dhama K, Singh KP, Tripathi BN. Pathological, immunological and molecular epidemiological analysis of lumpy skin disease virus in Indian cattle during a high-mortality epidemic. Veterinary Quarterly. 2024 Dec 31;44(1):1-22. https://www.tandfonline.com/doi/pdf/10.1080/01652176.2024.2398211