Is it true that epidemiologists use a unit called “hourly” to estimate the number of ticks?

There is popular information on the Internet that in epidemiology there is a unit of measurement per hour - this is the name for the number of ticks that in 60 minutes. collected on its body by a hedgehog released into the wild. We checked whether this practice is actually applied.

They write about the inventive use of hedgehogs in epidemiology sites with interesting facts, entertainment users portals, social networks And services questions and answers. Not are lagging behind from them and the Russian media: from newspapers Moscow district Mozhaisky and portal Regions.ru to "Ogonyok"and TV channel Ren-TV. Some people talk about the unusual unit of measurement in interviews. biologists - however, sometimes they notethat this method is no longer used.

Relationship between hedgehogs and ticks - example complex ecosystem relationship between vertebrates and their ectoparasites. Hedgehogs become hosts for different types of ticks, which use their bodies for feeding and spreading. Usually hedgehogs are infected with several types of mites at once, mainly such as Ixodes hexagonus (hedgehog mite) and Ixodes ricinus, as well as others representatives of the genus Rhipicephalus. These arthropods go through all stages of development on the body of hedgehogs and can carry infectious agents, including those dangerous to humans and domestic animals. Intensity of infection in hedgehogs depends from the habitat, the sex of the animal (males are usually more susceptible to it than females), as well as the seasonal activity of ticks. 

Examining these mammals and counting the parasites removed from them is a relatively popular method in epidemiological studies. In recent years they have been carried out, for example, in Spain, Poland And Pakistan, where biologists found an average of about 1.5 to 7 ticks on one hedgehog. However, the methodology of these scientists differs significantly from the one behind the concept of “every hour”. Firstly, in all these studies, hedgehogs were not released into the wild, but, on the contrary, were caught for study. Secondly, these hedgehogs collected ticks on themselves not for an hour, but throughout their entire lives before meeting the biologists. Moreover, there is simply no English-language concept corresponding to the hourly hour in foreign academic literature. 

It can be assumed that this method of studying parasites exists only in Russia. The main documents regulating the work of epidemiologists when collecting blood-sucking arthropods in natural foci of infections in the Russian Federation are “Methodological instructions 3.1.3012-12" and SanPiN 3.3686-21 “Sanitary and epidemiological requirements for the prevention of infectious diseases.” According to these documents, specialists can collect ticks from animals caught for this purpose or their corpses, as well as catch parasites by setting traps in hedgehog holes. There are also methods such as a drag (the collector slowly pulls a piece of plain, light-colored fleecy fabric over the area under study) and a flag (in this case, a piece of fabric is mounted on a pole). Sometimes ticks are collected “for live bait” - one of the researchers acts as bait, and then his colleagues collect parasites from his clothes. Depending on what exactly specialists are interested in - the prevalence of ticks in the area or the rate of their collection - they can use units of measurement such as flag/hour, flag/km, person/hour or person/km. Other important quantitative parameters are the abundance index (the average number of individuals of one species found on a piece of fabric or collector) and the occurrence index (the proportion of objects on which parasites were found out of the total number examined). Nothing is said in the regulatory documents about such a measure of measuring the number of ticks as hourly. 

In general, it is quite difficult to imagine collecting ticks using a method that allows you to calculate every hour. First, the animal must undergo training to exactly 60 minutes. move without interruption and then return to the starting point. Secondly, ticks of those species that usually spend their entire lives on the body of the same host, for some reason, must change their behavior and urgently begin to colonize the stranger.

First mention every hour on Google indexed sites dated 2003 Then this term appeared on the page “The hedgehog family (Erinaceidae)” in the “Biological Encyclopedia” on the portal dic.academic.ru. According to the current version of the site, the encyclopedia is based on several sources, including the six-volume Life of Animals, published by the Prosveshchenie publishing house in 1970. In the sixth volume of this encyclopedia, “Mammals, or Beasts,” there is the following fragment: 

In 1978 this term appeared in the magazine “Chemistry and Life” (No. 8), and in the early 1980s it was popularized by children’s writer-naturalist Stanislav Starikovich (for example, it is mentioned every hour in story “A Hedgehog is Not a Knight” from the collection “The Menagerie at the Porch”).

However, every hour did not arise out of nowhere - back in the work of the USSR Academy of Sciences “Livestock Pests: Work on Pyroplasma Vectors and Ectoparasites,” published in 1935, the authors wrote about the relationship between the number of ticks on the site and the number of these parasites on hedgehogs. "Verified" was unable to find the full text of this scientific work, but based on a fragment available in Google Books, it is possible assume, that we are still not talking about trained hedgehogs released into nature for exactly 60 minutes.

In other words, the most likely scenario for the appearance of the hourly clock is this: biologists, knowing that collecting ticks from hedgehogs is a very real method of counting these parasites, came up with a comic concept, adding training, “running” and strict time tracking to the completely scientific practice. This scientific-looking definition then found its way into a major encyclopedia, children's literature, and decades later into the media and social media posts.

Thus, although hedgehogs are used to count the tick population, there is no unit of measurement called “every hour” in science, and, unfortunately, there are no trained hedgehogs who work in conjunction with epidemiologists and know how to meet deadlines.

Cover image: DALL-E

Not true

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