Platydemus manokwari, an introduced flatworm present in Hawai‘i, which can act as a paratenic host of the rat lungworm parasite and that has been implicated in causing rat lungworm disease in Okinawa.
Credit: Shinji Sugiura.
These days, I seem to be constantly reporting on yet another way Creationism's putative intelligent [sic] designer has found to make us sick and generally cause an increase in the suffering in the world - if you believe the Creationist disinformation about biology.
Here we have yet another example.
As though the rat lungworm, Angiostrongylus cantonensis, wasn't nasty enough, especially when it infects humans and destroys the brain, the divine malevolence has been busy finding new ways to make sure humans become infected with this nasty little nematode, as reported by researchers from the Pacific Biosciences Research Center, University of Hawaii at Mānoa, Honolulu, HI, USA and the Royal Veterinary College, London, UK, who combed through nearly 140 scientific studies to show that slugs and snails are far from being the only possible vectors of the disease.
These so-called, paratenic hosts include 32 species of freshwater prawns/shrimp, crayfish, crabs, flatworms, fish, sea snakes, frogs, toads, lizards, centipedes, cattle and pigs. Of these, at least 13 species of prawns/shrimp, crabs, flatworms, fish, frogs, toads, lizards, and centipedes have been associated with causing rat lungworm disease in humans.
Although these paratenic hosts can become infected, the parasites remain in their immature form until eaten by a rodent, when they mature. If one of these paratenic hosts or an intermediate host such as a slug or snail is ingested by a human, the parasite continues to develop but only up to a point. That point is when they are in the person's brain, moving around and feeding on brain cells, then they die. The resulting brain damage and inflammation as the immune systems tries to cope with the dead worms is the cause of the symptoms of rat lung worm disease. Not usually fatal, but the process and debility it causes can be prolonged.
Here is what the US Centre for Disease Control and Prevention (CDC) has to say about it:
What is Angiostrongylus cantonensis?The University of Hawai'i at Mānoa School of Ocean and Earth Science and Technology (SOEST) news release explains how the research was conducted during the COVID-19 pandemic:
Angiostrongylus cantonensis is a parasitic worm of rats. It is also called the rat lungworm. The adult form of the parasite is found only in rodents. Infected rats pass larvae of the parasite in their feces. Snails and slugs get infected by ingesting the larvae. These larvae mature in snails and slugs but do not become adult worms. The life cycle is completed when rats eat infected snails or slugs and the larvae further mature to become adult worms.
Can people get infected with this parasite?
Yes. People can get infected, under unusual circumstances. However, even if infected, most people recover fully without treatment.
How can people get infected?
People can get infected by eating raw or undercooked snails or slugs that are infected with this parasite. In some cultures, snails are commonly eaten. Some children, in particular, have gotten infected by swallowing snails/slugs “on a dare. ” People also can get infected by accident, by eating raw produce (such as lettuce) that contains a small snail or slug or part of one.
Certain animals such freshwater shrimp, crabs, or frogs, have been found to be infected with larvae of the parasite. It is possible that eating undercooked or raw animals that are infected could result in people becoming infected, though the evidence for this is not as clear as for eating infected snails and slugs. Of note, fish do not spread this parasite.
Learn more about how people get infected with Angiostrongylus cantonensis in this new motion graphic video.
Can an infected person infect other people?
No.
In what parts of the world have people become infected with this parasite?
In many parts, but most of the known cases of infection have been in parts of Asia and the Pacific Islands. Some have been in other areas of the world, such as in the Caribbean and Africa.
Have cases of this infection occurred in the United States?
Yes. Cases have occurred in Hawaii (and other Pacific Islands). Very few cases have been reported in the continental United States. In 1993, a boy in New Orleans got infected by swallowing a raw snail “on a dare. ” The type of snail he swallowed isn’t known. He became ill a few weeks later, with muscle aches, headache, stiff neck, a slight fever, and vomiting. His symptoms went away in about 2 weeks, without treatment of the infection.
Can giant African land snails be infected with this parasite?
Yes. This type of snail, which can grow larger than a person’s hand, is just one of many types that can be infected. But snails can be infected only if they have ingested contaminated rat feces. We don’t know if any of the giant African land snails in the continental United States are infected.
What are the signs and symptoms of infection with this parasite?
Some infected people don’t have any symptoms — or have only mild symptoms that don’t last very long. Sometimes the infection causes a rare type of meningitis (eosinophilic meningitis). The symptoms can include headache, stiff neck, tingling or painful feelings in the skin, low-grade fever, nausea, and vomiting.
What should I do if I think I might be infected with this parasite?
You should see your health care provider, who will examine you and ask about any symptoms, travel, and exposures you’ve had (for example, to snails/slugs). You might have some blood tests, as well as tests for meningitis.
Does infection with this parasite need to be treated?
Usually not. The parasite dies over time, even without treatment. Even people who develop eosinophilic meningitis usually don’t need antiparasitics. Sometimes the symptoms of the infection last for several weeks or months, while the body’s immune system responds to the dying parasites. The most common types of treatment are for the symptoms of the infection, such as pain medication for headache or medications to reduce the body’s reaction to the parasite, rather than for the infection itself. Patients with severe cases of meningitis may benefit from some other types of treatment.
How can I keep from getting infected with this parasite?
Don’t eat raw or undercooked snails or slugs, frogs or shrimp/prawns. If you handle snails or slugs, wear gloves and wash your hands. Always remember to thoroughly wash fresh produce. When travelling in areas where the parasite is common, avoid eating uncooked vegetables.
This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.
This work was the master’s degree thesis research of the first author, Helena Turck, as part of a graduate program in One Health jointly run by the Royal Veterinary College and the London School of Hygiene and Tropical Medicine, both part of the University of London, UK. Robert Cowie, senior author on the study and faculty member in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), supervised Turck’s research remotely during the pandemic and co-authored the new publication. Professor Mark Fox of the Royal Veterinary College is also a co-author of the study.
Cowie explained that the rat lungworm has a complex life cycle that involves slugs and snails as so-called “intermediate” hosts and rats as “definitive” hosts in which the worms reach maturity and reproduce. Rats and people become infected when they eat an infected snail or slug. This can lead to serious illness and occasionally death.But people can also get infected if they eat so-called paratenic hosts, which are also known as carrier hosts. These are animals that become infected by eating infected snails or slugs, but in which the worms cannot develop to maturity as they do in a rat. However, in such hosts the worms become dormant, but still infective. And if one of these hosts, or part of one, is then eaten raw by a person – an accidental host – development can continue, but only up to a point.
It is important to know not only that snails and slugs can transmit rat lungworm parasites to humans but also which other animals – which paratenic hosts – can also do so, so the goal of the study, was to pull all the information on paratenic hosts and their role in transmission of rat lungworm disease, previously scattered in diverse publications and obscure reports, together into one place and develop a global understanding of their diversity and role in disease transmission.
Several species capable of acting as carriers (paratenic hosts) are present in Hawai‘i, including flatworms, centipedes, coqui frogs, and cane toads. While people in Hawai‘i are unlikely to eat these animals, it is not unknown for people to do so on a dare, and become seriously ill. Elsewhere, certain paratenic hosts are eaten for supposed health reasons – frogs in Taiwan and Japan, or to enhance virility – lizards in Thailand.
Robert H. Cowie, corresponding author
Pacific Biosciences Research Center
University of Hawaii, Honolulu, HI, USA
Humans, accidental hosts
That point is when they are in the person’s brain, where they are moving around, feeding, and growing. But then the worms die. The damage to the brain and the massive inflammation that results when they die is primarily what causes the symptoms of rat lungworm disease.
Rat lungworm disease around the globe
Rat lungworm disease is at present confined largely to the tropics and subtropics, notably parts of South and Southeast Asia, where it probably originated, southern China, Taiwan, southern Japan, various Pacific islands and archipelagos, and more recently Brazil, Caribbean islands, and Australia. The parasite has also been reported from the Canary Islands and Balearic Islands of Spain, as well as southeastern parts of the United States, where there have been a handful of cases of rat lungworm disease. Climate change may lead to its further spread into currently more temperate regions.
Hawai‘i is a global center of the incidence of rat lungworm disease, and indeed it was in Hawai‘i where the connection between the parasite and the disease was first discovered, by University of Hawai‘i and US government scientists in the early 1960s.
Domestic animals, especially dogs and horses, can also become infected by the rat lungworm parasite, including in Hawai‘i, probably mostly from accidentally or deliberately eating snails or slugs.
HighlightsCreationists must be wondering if there is a limit to the inventive nastiness of their favourite pestilential malevolence as it finds ever more ways to make humans and other animals suffer with its intelligently [sic] designed parasites and the creative designs it comes up with to ensure they infect their target victims.
- Neuroangiostrongyliasis, an emerging parasitic disease of humans and wildlife.
- Caused by the nematode Angiostrongylus cantonensis (rat lungworm).
- Infection primarily via ingestion of stage 3 larvae of the parasite.
- People eat raw intermediate or paratenic hosts infected with stage 3 larvae.
- Comprehensive review of paratenic hosts’ role in neuroangiostrongyliasis globally.
Abstract
The nematode parasite Angiostrongylus cantonensis (rat lungworm) has a complex life cycle involving rats (definitive hosts) and gastropods (intermediate hosts), as well as various paratenic hosts. Humans become infected and develop rat lungworm disease (neuroangiostrongyliasis) when they consume intermediate or paratenic hosts containing the infective parasite larvae. This study synthesizes knowledge of paratenic hosts of A. cantonensis and investigates their role in causing human neuroangiostrongyliasis worldwide. A literature review was conducted by searching PubMed, JSTOR and Scopus, pooling additional information from sources accumulated over many years by RHC, and snowball searching. The review identified 138 relevant articles published between 1962 and 2022. Freshwater prawns/shrimp, crayfish, crabs, flatworms, fish, sea snakes, frogs, toads, newts, lizards, centipedes, cattle, pigs and snails were reported to act as paratenic hosts in various regions including South and Southeast Asia, Pacific islands, the USA and the Caribbean, as well as experimentally. Human cases of neuroangiostrongyliasis have been reported from the 1960s onwards, linked, sometimes speculatively, to consumption of freshwater prawns/shrimp, crabs, flatworms, fish, frogs, toads, lizards and centipedes. The potential of paratenic hosts to cause neuroangiostrongyliasis depends on whether they are eaten, how frequently they are consumed, the preparation method, including whether eaten raw or undercooked, and whether they are consumed intentionally or accidentally. It also depends on infection prevalence in the host populations and probably on how high the parasite load is in the consumed hosts. To prevent human infections, it is crucial to interrupt the transmission of rat lungworm to humans, from both intermediate hosts and frequently consumed paratenic hosts, by adhering to safe food preparation protocols. Educating the general public and the medical community about this largely neglected tropical/subtropical disease is key.
Turck, Helena C.; Fox, Mark T.; Cowie, Robert H. (2022)
Paratenic hosts of Angiostrongylus cantonensis and their relation to human neuroangiostrongyliasis globally
One Health 15 100426; DOI: 10.1016/j.onehlt.2022.100426
Copyright: © 2022 The authors.
Published by Elsevier B.V. Open access
Reprinted under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license (CC BY-NC-ND 4.0)
To evolutionary biologists, on the other hand, there is a simple explanation for the origins of these parasites and their methods of transmission which doesn't involve magic gods and does not involve sentience, so there is no question of malevolent intent. The extraordinary thing is that creationist frauds would rather their dupes had the view that their putative creator god is a malevolent, pestilential monster than that they accept the scientific view, so it isn't hard to work out that they have a political objective which doesn't involve regarding an assumed deity as an all-loving, omnibenevolent force for good, but as an object of fear and loathing.
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