Echinococcus Equinus Found in Imported Donkeys: What the Ejiao Industry Needs to Know

Trade routes have always carried more than goods. They move animals, and the pathogens those animals carry. A recent study shows how that plays out in real time.

Researchers at a port slaughterhouse in northwestern China examined 1,900 donkeys imported from Kyrgyzstan between November 2023 and February 2024. What they turned up is worth paying attention to.

A Parasite Worth Knowing

Echinococcus equinus (genotype G4) is a tapeworm that causes cystic echinococcosis — a parasitic disease where fluid-filled cysts form in the liver, lungs, and other organs. The WHO lists it among the neglected tropical diseases.

The life cycle works like this. Adult tapeworms live in the intestines of dogs, foxes, and jackals. Those animals shed eggs in their feces. When horses or donkeys graze on contaminated ground, they swallow those eggs. The larvae hatch, burrow through the intestinal wall, and form hydatid cysts — mostly in the liver and lungs. People get infected the same way: ingesting eggs from contaminated food, water, or from handling infected dogs.

Until this study, E. equinus had been documented in Europe (UK, Ireland, Italy, Spain, Switzerland, Germany), Africa (Namibia, Kenya), and parts of West Asia (Turkey). Central Asia was a blank spot.

What They Found

The team collected 52 hydatid cysts from 18 infected animals out of 1,900 donkeys. That’s 0.9%. Most cysts were in the liver alone. One donkey had cysts in both the liver and lungs. They ranged from half a centimeter to 8 centimeters across.

They confirmed the parasite’s identity using two methods.

First, molecular fingerprinting. They sequenced two mitochondrial genes (cox1 and nad1) from all 52 cysts. Every sample came back as E. equinus — 100% identical to strains from dogs in Kyrgyzstan, donkeys and wolves in Turkey, zebras in Namibia, and horses in the UK.

Second, whole mitochondrial genome sequencing. They sequenced the complete circular mitochondrial genome from one cyst. It came out to 13,722 base pairs and was 99.98% identical to a UK horse strain. So the Central Asian strain is genetically almost identical to what you’d find in Europe.

Then They Tested Mice

The researchers wanted to know whether this strain could infect non-equine hosts. Could it jump species more easily than assumed?

They injected 18 C57BL/6 mice with protoscoleces — the larval stage — harvested from the donkey cysts. After 180 days, three out of 18 mice (about 17%) developed hydatid cysts. One mouse had a visible cyst about a centimeter wide in its liver. Two others had smaller cysts in both the liver and intestinal lining.

The smallest dose that caused an infection was 1,210 protoscoleces with about 34% fertility. That’s not a huge number.

This matters because it’s direct experimental evidence that E. equinus can infect non-equid hosts. Until now, that had only been seen occasionally in lemurs and humans.

Why Infected Donkeys Matter

Ejiao — a traditional Chinese medicine ingredient made from donkey hide — is driving this whole thing.

Demand for Ejiao has exploded. China’s donkey population has collapsed from over 11 million in the 1990s to about 1.46 million in 2023. So China imports donkeys. A lot of them. Kyrgyzstan sent 500 donkeys to China in 2023. That number jumped to 2,904 in 2024.

This study confirms those live imports can carry E. equinus.

Here’s the transmission chain in plain terms. Infected dogs in Kyrgyzstan shed eggs. Donkeys pick up the infection while grazing. Those donkeys get slaughtered at port facilities. Slaughterhouse waste and offal can feed local dogs or get dumped improperly. The cycle repeats somewhere new.

About 40% of Kyrgyzstan’s workforce is in agriculture and livestock. Close contact between dogs, livestock, and people in rural Central Asia creates plenty of transmission opportunities.

How This Changes Things

Before this study, the evidence for E. equinus in Central Asia was spotty. A dog in Kyrgyzstan tested positive. A patient in Uzbekistan had an infection. But nobody had systematically checked the region’s livestock. This study fills that gap with solid molecular evidence.

The 0.9% figure is also probably an underestimate. Port inspections rely on visual checks of organ surfaces during slaughter. Small or deeply embedded cysts get missed. There’s no reliable blood test for detecting Echinococcus in live horses or donkeys. Ultrasound isn’t practical for large-scale customs quarantine.

What Comes Next

Diagnostic methods for E. equinus in livestock need to catch up. Visual inspection at slaughter is better than nothing, but it’s not enough when dealing with a parasite that can infect people.

The transboundary angle matters too. The same strain found in Kyrgyzstan donkeys matches strains from Europe, Africa, and West Asia. That means E. equinus is widely distributed and moves with its hosts across continents.

The Ejiao supply chain is a real pathway for disease spread. As China taps more countries for donkey imports, each new source brings its own infectious disease profile. Monitoring has to keep pace.

The Honest Limitations

The researchers were upfront about their blind spots. Abattoir surveillance misses plenty of infections. The mouse experiment was a preliminary test, not a full infection model. And reliable large-scale screening tools for equids simply don’t exist for customs use yet.

The core finding stands anyway: E. equinus is in donkeys entering China from Kyrgyzstan, and it can infect non-equid hosts in the lab.

Three Takeaways

1. First molecular confirmation of E. equinus in Kyrgyzstan-imported donkeys, backed by complete mitochondrial genome sequencing.
2. Lab evidence that this strain infects mice, confirming cross-species capability.
3. The Central Asian strain is genetically almost identical to European strains, suggesting a widespread distribution.

For anyone tracking emerging infectious diseases, livestock trade, or food safety — these findings are worth keeping an eye on. The donkeys crossing borders carry more than hides and meat. They carry parasites we still don’t fully understand.