The strange case of the weaned piglets "suddenly dying" in the nursery

The news provides an in-depth clinical case study on the sudden deaths of weaned piglets in a nursery facility, authored by Dr. Giampietro Sandri, DVM. The focus is on diagnosing and managing an outbreak of unexplained mortality among seemingly healthy piglets.

Overview of the Farm and Setup

The farm consists of three nursery compartments, each with 29-30 pens holding 25-30 pigs. The flooring varies between cement and plastic slats, and the ventilation system is semi-natural. The farm is generally well-maintained with a medium-high level of hygiene. The herd includes 630 sows, with a batch farrowing system of approximately 80 sows per group. Piglets are weaned at 24-28 days of age and weigh between 6.6 to 7.2 kg. Vaccinations for the herd include PPV (Porcine Parvovirus) and Erysipelas, administered at the end of lactation. Other preventive treatments include ivermectin for parasite control, and limited use of antibiotics like amoxicillin.

Initial Problem

On November 15, the farmer reported several sudden deaths among healthy-looking piglets in compartment C. The following day, a veterinary inspection revealed no specific clinical symptoms like coughing or diarrhea. The piglets appeared healthy, were eating normally, and the environment, waterers, and feeders were in good condition. A necropsy was performed on two deceased piglets, but no distinct pathological lesions were found. Tissue samples were sent to the laboratory for further analysis.

Escalation of the Issue

Over the next two days, additional piglet deaths occurred without any central nervous system symptoms, prompting a treatment plan of administering amoxicillin in water at a dosage of 20 mg/kg body weight. While initially effective, the farmer reported more deaths in other compartments, bringing the total mortality rate up to 25% by the end of the nursery period.

Differential Diagnosis

Several potential causes of the sudden deaths were considered, including:

• Streptococcus suis infections
• Septicemia caused by E. coli
• Haemophilus parasuis infection
• Other possibilities such as viral myocarditis caused by the foot-and-mouth disease virus, also referred to as "Kitt's tiger-like heart."

Laboratory Findings

Histopathological examination revealed venous congestion in the right side of the brain, massive enlargement of the right ventricle, and necrosis of the myocardium. These findings suggested acute heart failure, potentially linked to a viral cause.

Focus on Encephalomyocarditis Virus (EMCV)

The news shifts focus to EMCV, a picornavirus transmitted primarily through rats, which serve as a long-term reservoir. Piglets are infected through ingestion of contaminated materials, including dead rats, or through environmental contamination from rat urine or feces. Once infected, piglets typically die within 2-11 days, with an average of 4.5 days. The most common sign is sudden death, often triggered by minor stress or movement, with few other observable symptoms. Lesions typically involve the enlargement of the heart, particularly the right side, along with white necrotic areas in the myocardium.

Management and Control Measures

After identifying the likely cause of death, drastic biosecurity measures were implemented:

• The nursery was completely emptied.
• Comprehensive cleaning and disinfection were carried out.
• Rodent control was intensified, with aggressive pest control measures put in place.
• Thermofogging of the compartments was used to ensure complete disinfection.

The case study emphasizes the importance of rodent control in preventing viral outbreaks like EMCV, as well as the need for vigilant observation and early intervention when sudden deaths occur in piglets.

Conclusion

This news highlights the complex nature of managing sudden mortality in piglets. Despite good farm management practices, the presence of viral agents like EMCV, transmitted by rodents, can lead to devastating losses. The farm’s response, which included enhanced biosecurity, pest control, and thorough disinfection, is crucial to controlling and preventing further outbreaks.