A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
We report an outbreak of infections with a novel protoparvovirus on several commercial farms in the Netherlands and associations with a clinical syndrome in pigs characterized by exophthalmos and erythema. Evidence of involvement of this virus, highly similar to a vulpine parvovirus, was substantiated by long-read sequencing and in situ hybridization techniques.
Parvoviruses are small, nonenveloped viruses with a single-stranded negative sense DNA genome ( 1 ). They are ubiquitous and infect a wide variety of hosts; disease manifestations range from subclinical to lethal ( 1 ). In pigs, 8 porcine parvoviruses (PPVs; PPV1–PPV8) are known; PPV1 is the species with established pathogenicity and is a major cause of reproductive disorders in pigs worldwide ( 2 – 4 ). Causal disease inference for other PPVs is challenging and requires a combination of virus detection and in situ hybridization (ISH), especially when histologic lesions are limited to nonexistent ( 3 ).
Figure 1 . Case (left) and healthy control (right) piglets of ≈2.5 weeks of age in study of multifarm outbreak of novel parvovirus in pigs associated with exophthalmos and erythema, the Netherlands, 2024....
In December 2024, piglets (1–4 weeks of age) on 2 separate pig farms in the Netherlands displayed variable degrees of bilateral exophthalmos and strabismus and signs of erythema and alopecia ( Figure 1 ). The cases were reported to Royal GD (Deventer, the Netherlands) as part of the national animal health surveillance program ( 5 ). All investigations on animals and animal tissues for this work were conducted under veterinary supervision for purpose of appropriate animal care and diagnostics, according to the Dutch Act on Animals, thereby exempt for ethical approval under the Dutch Experiments on Animals Act and EU Directive 2010/63/EU. Samples from control animals were obtained as part of another study for educational purposes at Utrecht University (animal welfare license number AVD10800202215910). The owners of the animals consented to all performed activities for this case report.
By August 2025, the number of farms reporting piglets showing those unusual clinical signs had increased to >80. Although the initial case farms indicated evidence of growth retardation, clinical findings had remarkably reduced after 3 to 4 months without applying specific interventions and without marked increase of death. Postmortem investigations were performed to study the underlying cause. Gross pathology of 20 piglets from 7 affected farms did not provide any conclusive results. Microscopic lesions were mostly absent or inconclusive. Finally, routine laboratory diagnostics for underlying nutritional or toxicological causes and molecular testing for common pig pathogens, including PPV1, were either negative or inconsistent.
To identify a putative causative agent causing the unusual signs, we isolated nucleic acids from different tissues of 18 affected piglets and 4 nonaffected piglets ( Appendix ) and analyzed those nucleic acids by nontargeted Oxford Nanopore Technology ( https://nanoporetech.com ) sequencing and virus metagenomics using an in-house virus…