Hedgehogs reveal the presence of an unknown parasite in Mallorca: the rat lungworm

The distribution of a lesser-known parasite, the rat lungworm, appears to be increasing – its discovery in Mallorcan hedgehogs led Dr Paredes-Esquivel and his team to investigate its transmission on the island.

Under the microscope, woman Angiostrongylus cantonensis have a distinctive feature that makes them instantly recognizable and fascinating to look at: white uterine tubes and intestines filled with red blood intertwine along the body of the nematode, resulting in a hairdresser sign or barley sugar appearance. Male worms, on the other hand, are identified by a copulatory terminal bursa that resembles a delicate mantle surrounding a few short tentacles. Together they make a happy couple of rat lungworms.

Adult female worm Angiostrongylus cantonensis with a characteristic appearance of barber poles The scale bar is 1 mm. Photo credit:
John F. Lindo, Cecilia Waugh, John Hall, Colette Cunningham-Myrie, Deanna Ashley, Mark L. Eberhard, James J. Sullivan, Henry S. Bishop, David G. Robinson, Timothy Holtz and Ralph D. Robinson, public domain, via Wikimedia Commons

Rats, as definitive hosts, harbor these nematodes in their lungs; the worms are spat out, swallowed and eventually passed out in the rat’s feces. Slugs or snails (intermediate hosts) are infected by ingesting rat waste. These gastropods, in turn, are part of the rat’s regular menu, so the cycle is maintained.

But like many parasites, the rat lungworm often finds its way to other animals, including freshwater prawns, crabs and frogs – accidental hosts. Humans are infected by consuming undercooked dishes with one of these hosts, which can be part of many cuisines around the world, or by unwashed contaminated products (such as raw salads). The initial symptoms of the disease may be nonspecific, such as abdominal pain, nausea, and vomiting. In some cases, the parasites can reach the brain and cause eosinophilic meningitis. When the central nervous system is compromised, symptoms worsen into chronic debilitating migraines, impaired vision and hearing, and skin burning sensation and pain, among others. Diagnosis can be difficult, and patients with the first clinical signs of lungworm infection in rats have been misdiagnosed as having influenza or non-threatening illness. About 2,800 cases have been reported until 2008; Although there are no published updates of the cases to date, they are likely to have significantly increased with frequency of travel worldwide.

The suffering of angiostrongylosis goes beyond the disease itself – as patients are unable to work and are unable to work, families are also affected when they have to become full-time caregivers, and loss of life. incomes follow. Animal infections can result in euthanasia of pets and livestock. Recognition of lung worm disease in rats by healthcare professionals is essential to initiate timely treatment and reduce the severity of sequelae.

Humans can ingest A. cantonensis by consuming undercooked snails, freshwater shrimp, frogs or crabs, or contaminated products. Symptoms of eosinophilic meningitis can be varied and severe. Credit K. Mondragon-Shem

How did the rat lungworm get to Mallorca?

In the beautiful island of Mallorca, millions of tourists bask in the sun, a lazy sea lapping at their feet, while gazing at the blue-green hues that stretch between them and the horizon. It is in this popular destination that Dr. Claudia Paredes-Esquivel and his team are carrying out their work as part of a research group on animal conservation at the University of the Balearic Islands. His team studies pathogens in native wildlife and invasive species, often in collaboration with Wildlife Recovery Consortium (COFIB).

In October 2018, COFIB admitted two North African hedgehogs with signs of serious damage to the central nervous system. As the hedgehogs had lost the ability to control their limbs and mouth, both were euthanized to prevent further suffering. After some detective work involving delicate necropsies, The Paredes-Esquivel team discovered little hairdresser sign nematodes in the brains of two hedgehogs. Further molecular analyzes confirmed their initial suspicions: both animals had been infected with A. cantonensis. “Other infected hedgehogs have since been discovered, and the evidence suggests that there is active transmission of the disease in Mallorca,” says Dr Paredes-Esquivel, “I believe this is part of a larger problem. which urgently needs to be resolved ”.

Although neurological symptoms have already been noticed in island hedgehogs, a Angiostrongyle infection was never suspected because: 1) angiostrongylosis has never been reported on the island and 2) hedgehogs have never been identified as a host species before. One of the most important discoveries of the group was the presence of sexually mature worms in the hedgehog’s brain. Yes A. cantonensis reproduce only in the definitive host, does this mean that hedgehogs are now part of this parasite’s life cycle? This is a key question that Dr. Paredes-Esquivel and her colleagues are trying to answer. They are also studying how this parasite got to the island, what role hedgehogs and other animals play in the worm’s life cycle, and more importantly, what the disease risks are for residents and visitors to the island. .

For a relatively unknown parasite, the rat lungworm has a surprisingly wide distribution that includes dozens of cities on almost every continent. And now Mallorca. It is well known that the constant sea and air traffic to Mallorca, fueled mainly by millions of tourists every year, increased invasive species in the island. COFIB launched a “ hotline ” application which, in six months, received reports from more than 500 invasive species in the Balearics. This has likely included infected rats and snails on the island, and Mallorcan hedgehogs feeding on infected snails are susceptible to this invasive parasite.

Human angiostrongylosis prevention and control measures, according to CDC.gov. Credit K. Mondragon-Shem.

Preventative measures for those living in endemic areas, this should include proper handling of contaminated food and surfaces, and education of health workers and the general public about the risks of disease. While this story may lead some people to conclude that all hedgehogs are now dangerous, it certainly is do not the case. On the contrary, they are extremely valuable for disease surveillance, especially in fragile island ecosystems like Mallorca. Here, active surveillance for A. cantonensis infections will be a critical step towards controlling the spread of this invasive parasite around the island and will serve as an example for other places as this parasite continues to spread.

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