As soon as I first read about the recognition by physicians that that death from COVID-19 was often caused by a cytokine storm – a massive inflammatory response to an invader, which causes major tissue damage – my first thought was, “I wonder if people who have helminths on board will have more modulated immune responses and thus, be in less danger.” Honestly, I have been so busy, between working my two jobs, keeping up with this blog, caring for my son, house, and all the usual stuff, I never had time to follow up on that thought. Fortunately for all of us, I have a friend in the UK who keeps up on everything “helminth.” (For those who are really interested in delving deeply into helminths please take a little time to check out his incredibly comprehensive Wiki pages!) Tuesday morning, he sent me an email pointing out three new papers, all saying essentially the same thing: helminths seem to have a protective effect against COVID-19.
Paper 1: These researchers analyzed data from the WHO on both COVID-19 cases and helminths, as well as the parasitic malaria organism.[i] They found an inverse correlation between the incidence of the virus and malaria, and the virus and helminths. The more malaria in a country, the less likely to have cases of COVID. The higher the incidence of helminth infection in a country, the fewer the cases of COVID. Their hypothesis: the low incidence of COVID and death from COVID is the result of the immune modulation afforded by the presence of parasites (including both helminths and malaria). This is a correlation not a causation, obviously, but interesting to contemplate anyway, considering the immunology of helminth infection. See #2 and #3 below for more on that.
Paper 2: A second paper also examines the low incidence of COVID-19 in tropical and subtropical places in the world.[ii] Their hypothesis: the modulated inflammatory response of those with helminths, combined with the high levels of eosinophils provided by the presence of helminths “…is the perfect setting to avert both the infection with the COVID-19 virus and the Acute Respiratory Distress Syndrome (ARDS) that is the main cause of death from the disease.” The virus, they say, would be prevented by the action of the high levels of eosinophils, which have a strong effect against RNA-viruses while the inflammatory modulation would protect those infected against the cytokine storm, as mentioned in paper 1. Their summation: “…we believe that chronic helminth infection provides infected people with an unexpected wealth of protective mechanisms against the Covid-19 disease and its lethal complications. This can be suitably articulated using a two legged model, whereby eosinophils, as abundantly present in helminth infected people, by preventing the viral replication in the epithelia, would represent the first leg. The other leg in this model, the Th2-IL-10 system, would be of extreme importance, since it would avert the building up of the stormy uncontrolled auto-immune reaction as seen in the lungs during SARS.” My thinking exactly (see paragraph 1)!
Paper 3: This article[iii] is a short commentary that calls for the research community to consider the fact that since helminths have these anti-inflammatory/anti-viral effects, this is not the time to deworm human populations, as the effects of doing so may be highly detrimental.
Of course there are no research studies going on to actually test this hypothesis in the lab. It does make an awful lot of sense though and as you know, I’m all for doing sensible things that can be done now.
[i] Ssebambulidde, K, et. al. Parasites and their protection against COVID-19 ecology or immunology? medRxiv 2020.05.11.20098053; doi: https://doi.org/10.1101/2020.05.11.20098053 [not yet peer reviewed]
[ii] Carlos Rodriguez. (2020). The global helminth belt and Covid-19: the new eosinophilic link. Qeios. doi:10.32388/IWKQH9.2.
[iii] Bradbury RS, Piedrafita D, Greenhill A, Mahanty S. Will helminth co-infection modulate COVID-19 severity in endemic regions?. Nat Rev Immunol. 2020;20(6):342. doi:10.1038/s41577-020-0330-5