ASF vs Edema Disease: How to Tell the Difference in 60 Seconds

In a pig farming WhatsApp group this week, a farmer posted that his pig suddenly collapsed and died while running to eat. The first response was: "ASF is real oooo" — panic spread through the group. Farmers started mentally culling their herds. Then an experienced farmer looked at the photo, saw swollen eyelids, and correctly diagnosed Edema Disease — a bacterial infection that is completely treatable with Atropine + Sulphadimidine + Procaine.

This confusion happens every day in farming groups across Africa. African Swine Fever (ASF) has no cure and requires culling the entire herd. Edema Disease is treatable and the rest of the litter can be saved. The difference in outcome is catastrophic — and it comes down to a 60-second diagnostic that every pig farmer must know [1][2].

Why this matters so much

ASF is a viral hemorrhagic disease with mortality rates of 90-100% in acute form. There is no vaccine, no treatment, and no cure. If ASF is confirmed on your farm, the only option is to cull the entire herd, disinfect everything, and rest the farm for 90+ days. The economic loss is total.

Edema Disease is caused by Shiga-toxin producing E. coli bacteria [3]. It primarily affects weaned piglets 1-2 weeks after weaning. It causes sudden death, but the bacteria responds to antibiotic treatment. If caught early, 70-90% of affected piglets can be saved. The economic loss is partial and recoverable.

If you misdiagnose Edema Disease as ASF and cull your entire herd, you have just destroyed a recoverable situation. If you misdiagnose ASF as Edema Disease and start treating with antibiotics, you have wasted time while ASF spreads to every pig on the farm. Both errors are catastrophic.

The 60-second diagnostic

Look at the sick or dead pig. Check these 5 things:

1. Are the eyelids swollen? Yes → Edema Disease. No → continue.
2. Are multiple pigs sick at the same time? Yes (5+ pigs in 48 hours) → suspect ASF. No (1-2 pigs) → suspect Edema Disease or other individual cause.
3. What is the age of the affected pigs? Weaners (4-10 weeks old, 1-2 weeks post-weaning) → Edema Disease most likely. All ages affected → ASF more likely.
4. Is there skin discoloration (red/blue/purple)? Yes, especially on ears, abdomen, legs → ASF. No skin discoloration, just swollen eyelids + staggering → Edema Disease.
5. Are the sick pigs staggering, with head tilt or incoordination? Yes → Edema Disease (neurological signs from the Shiga toxin). No neurological signs, just fever + depression → ASF.

Symptom comparison table

What is Edema Disease, exactly?

Edema Disease is caused by specific strains of E. coli that produce Shiga toxin 2e (also called verotoxin). The bacteria colonize the small intestine of weaned piglets, produce the toxin, which is absorbed into the bloodstream and damages blood vessel walls throughout the body — especially in the brain, eyelids, and subcutaneous tissue [3].

The damage to blood vessels causes fluid to leak into tissues, producing the characteristic swollen eyelids. The brain damage causes the staggering, head tilt, and incoordination. The toxin can kill the piglet within 24-48 hours of first symptoms, which is why the disease often presents as "sudden death."

The disease typically strikes 1-2 weeks after weaning because weaning stresses the piglet's digestive system, allowing the pathogenic E. coli to proliferate. It is also more common in piglets that have been on high-protein starter feed or have experienced sudden feed changes.

The Edema Disease treatment protocol

If you suspect Edema Disease (swollen eyelids + staggering weaner), act immediately:

1. Atropine sulfate: 0.04-0.08 mg per kg body weight, subcutaneously. Reduces secretions and counteracts the toxin's effects.
2. Sulphadimidine (sulfamethazine): 50-100 mg per kg body weight, IM or oral, daily for 3-5 days. This is the antibiotic that kills the E. coli producing the toxin.
3. Procaine penicillin: 10,000-20,000 IU per kg body weight, IM, daily for 3-5 days. Backup antibiotic to clear the E. coli infection.
4. Dexamethasone: 1-2 mg per kg body weight, IM, once daily for 2-3 days. Reduces the inflammation and edema.
5. Electrolytes with glucose: Oral, freely available. Prevents dehydration and provides energy.
6. Treat ALL pigs in the affected pen — not just the sick ones. The E. coli is spreading, and asymptomatic pigs are incubating.
7. Disinfect the pen with strong disinfectant after the outbreak. E. coli can persist in the environment.
8. Reduce feed protein by 2-3% for 1-2 weeks. High-protein feed favors E. coli proliferation.
9. Add zinc oxide to the feed (2,500-3,000 ppm) for 2 weeks. Zinc reduces E. coli adhesion to the intestinal wall.

With this protocol, 70-90% of affected piglets survive if treatment begins within 12 hours of symptom onset. After 24 hours, survival drops to 30-50%.

What to do if you suspect ASF

If you suspect ASF (multiple pigs, fever, skin discoloration, all ages affected, NO swollen eyelids):

1. Do NOT move any pigs off the farm. ASF is highly contagious and spreads through live pigs, pork products, contaminated feed, and even on boots and equipment.
2. Isolate the sick pigs immediately in a separate pen with no contact with other pigs.
3. Call the national veterinary service immediately. In most African countries, ASF is a notifiable disease — you are legally required to report it.
4. Send samples for diagnosis. A blood sample or tissue sample from a dead pig can confirm ASF within 24-48 hours at a national veterinary laboratory. Do NOT rely on field diagnosis alone — ASF and CSF (Classical Swine Fever) are clinically indistinguishable and require lab testing to differentiate [4].
5. Prepare for the worst. If ASF is confirmed, you will need to cull all pigs on the farm (and possibly contact farms within a quarantine zone). The government may provide compensation, but often does not.
6. Disinfect everything with 2% sodium hydroxide (lye) solution. Ordinary disinfectants like chlorine or iodine may not kill the ASF virus, which is unusually resistant.
7. Rest the farm for 90 days minimum after the last pig dies or is culled. The ASF virus can persist in the environment for months.
8. Notify neighboring farmers within 5km. They need to take immediate biosecurity measures.

The bottom line

If you take one thing from this article, take this: swollen eyelids = Edema Disease = treatable. Skin discoloration + multiple deaths = ASF = notifiable, cull, disinfect. The 60 seconds you spend checking these two signs can save your entire herd — or, if you get it wrong, doom it.

When in doubt, do not rely on WhatsApp group diagnosis alone. Send a sample to the nearest veterinary laboratory. The cost of a lab test (typically 5,000-15,000 FCFA, ~$8-25 USD) is trivial compared to the cost of misdiagnosis (losing your entire herd unnecessarily, or spreading ASF by failing to act).

Sources & References

• [1] WOAH (World Organisation for Animal Health): African swine fever — mortality 90-100% in acute form; no vaccine, no treatment. Source: woah.org
• [2] Merck Veterinary Manual: Edema Disease in Pigs — peracute vasculitis causing facial swelling, caused by Shiga toxin-producing E. coli. Source: merckvetmanual.com
• [3] PMC: Cross-sectional survey of risk factors for edema disease — caused by Shiga toxin-producing E. coli (EDEC) in the first few weeks after weaning. Source: pmc.ncbi.nlm.nih.gov
• [4] PMC: African and classical swine fever: similarities, differences — ASF and CSF are clinically indistinguishable and require laboratory testing to differentiate. Source: pmc.ncbi.nlm.nih.gov