Contagious Ecthyma: Diagnostic Approaches and Management of Affected Animals

Contagious ecthyma can often be recognized from its characteristic clinical presentation, but laboratory confirmation becomes important when lesions overlap with other diseases or when a definitive diagnosis is required. The diagnostic options described for orf range from electron microscopy and serological techniques to PCR-based methods, cell culture isolation and virus neutralization testing. Once affected animals are identified, management focuses on separation, supportive care and attention to secondary bacterial infection. 

Laboratory Diagnosis: Choosing the Appropriate Approach¹ 

Several laboratory examinations can be used for contagious ecthyma, including electron microscopy (EM), agar gel precipitation test, agglutination testing, complement fixation testing, serum neutralization testing, enzyme-linked immunosorbent assay (ELISA), PCR, and restricted fragmented length polymorphism (RFLP) analysis. 

Electron Microscopy 

Electron microscopy is described as a rapid method for diagnosing and distinguishing poxvirus infections. Parapoxvirus particles have an ovoid appearance with external tubules arranged in a crisscross pattern resembling a ball of yarn. This morphology can help distinguish parapoxviruses from other poxvirus genera and viruses, making EM useful for initial diagnosis¹. 

However, EM does not identify the virus at a species level. Its limitations also include low sensitivity, requiring a minimum of 106 particles per ml, together with limited availability of suitable facilities and trained personnel². 

ELISA and PCR 

ELISA permits rapid screening of large numbers of samples using plates coated with purified orf viral antigens and antibodies, with peroxidase-conjugated protein A or protein AG. It has been effective for diagnosing ORFV infection in humans and parapoxvirus infections in California lions^1,3. 

PCR provides a more targeted molecular approach. For ORFV, the genes most frequently used for diagnosis are B2L (ORFV011) and FIL (ORFV059). The technique amplifies selected DNA sequences through repeated cycles of denaturation, annealing and extension using thermostable DNA polymerase. The identity of the amplified product can subsequently be validated through DNA hybridization¹. 

Real-Time PCR and Virus Isolation 

Real-time PCR monitors the accumulation of amplified PCR product during the reaction and can be used to determine the amount of DNA present in a sample. The development of portable real-time PCR devices and assays has also raised the possibility of rapid diagnosis during field outbreaks. The described assay uses the B2L major envelope gene of ORFV^1,4. 

For virus isolation, several cell systems can be used, including primary lamb testis, lamb kidney, fetal lamb dermis and muscle, fetal bovine muscle and lung cells, as well as MDBK, MDOK and Vero cells. Cytopathic effects may appear as ballooning, rounding and cell degeneration after one to two passages¹. 

Virus neutralization testing detects virus-specific antibodies following natural infection or vaccination. However, because ORFV infection is associated predominantly with cell-mediated immune responses and low concentrations of neutralizing antibodies, serum neutralization is not commonly used for ORFV diagnosis⁵. 

Management of Affected Animals 

During outbreaks, newly introduced animals should be isolated before integration into the herd. Sick animals should be separated from the herd, nourished and treated. The source specifically mentions ceftriaxone and tazobactam for affected goats and notes that herbal injections or aerosol sprays can be applied to affected areas. 

Milk from animals with sores on their teats should not be consumed. Because people can acquire the disease from affected animals, gloves and facemasks should be used while handling sick animals and administering vaccinations. The source also advises against administering a live-virus vaccine on a farm where an outbreak has previously occurred because vaccine virus may spread into the surrounding area¹. 

Key Takeaway 

For veterinary practice, diagnostic selection should reflect the purpose of confirmation and the capabilities available. EM can support initial parapoxvirus recognition, ELISA permits large-scale screening, PCR targets specific ORFV genes, real-time PCR offers quantitative detection with potential field applications, while cell culture can support virus isolation. Management requires separation of affected animals, supportive attention and precautions against transmission to people. 

References 

1. Bhagawati N, Shankarishan P, Habibi M. Contagious ecthyma in goat and sheep: a review of current status and future perspectives. Uttar Pradesh J Zool. 2025;46(10):229-239. doi:10.56557/UPJOZ/2025/v46i104982. https://mbimph.com/index.php/UPJOZ/article/view/4982/6394 

2. Hosamani M, Scagliarini A, Bhanuprakash V, McInnes CJ, Singh RK. Orf: an update on current research and future perspectives. Expert review of anti-infective therapy. 2009 Sep 1;7(7):879-93. https://www.academia.edu/download/41885833/Orf_An_update_on_current_research_and_fu20160202-30232-6wkxr.pdf 

3. Nollens HH, Jacobson ER, Gulland FM, Beusse DO, Bossart GD, Hernandez JA, Klein PA, Condit RC. Pathology and preliminary characterization of a parapoxvirus isolated from a California sea lion (Zalophus californianus). The Journal of Wildlife Diseases. 2006 Jan 1;42(1):23-32. https://bioone.org/journals/Journal-of-Wildlife-Diseases/volume-42/issue-1/0090-3558-42.1.23/PATHOLOGY-AND-PRELIMINARY-CHARACTERIZATION-OF-A-PARAPOXVIRUS-ISOLATED-FROM-A/10.7589/0090-3558-42.1.23.pdf 

4. Gallina L, Dal Pozzo F, Mc Innes CJ, Cardeti G, Guercio A, Battilani M, Ciulli S, Scagliarini A. A real time PCR assay for the detection and quantification of orf virus. Journal of Virological Methods. 2006 Jun 1;134(1-2):140-5. https://www.academia.edu/download/43812378/A_real_time_PCR_assay_for_the_detection_20160317-32411-xwzmd1.pdf 

5. Krešić N, Šimić I, Bedeković T, Acinger-Rogić Ž, Lojkić I. Evaluation of serological tests for detection of antibodies against lumpy skin disease virus. Journal of clinical microbiology. 2020 Aug 24;58(9):10-128. https://journals.asm.org/doi/pdf/10.1128/jcm.00348-20