Parasites in the Human Body, Temperate Climate – Part 1

“Intelligence is based on how efficient a species became at doing the things they need to survive.”

“Parasitism is the highest form of predatory behavior”.  Charles Darwin

The human species have always been a host to parasites, and along with the migration of humans, parasites too have managed to spread and adapt to hard-to-survive habitats.  Global statistics about parasite-infected humans is terrifying and although the people in the more advanced states are more capable of tackling the problem of parasites, they tend least to pay attention to it.  The poor population of countries such as Somalia, Zimbabwe, and India for a very long time now is born with parasites in their bodies and is constantly seeking ways to get free of them.  Certainly, the living conditions in such counties perpetuate a cycle of infectious cysts and larvae coming in the host organism and leaving it in a diagnostic stage.

Water for household use is treated across Europe, and at the same time the demand for organic food there is strongest.  In other words, there is no way that you get parasites while brushing your teeth in Europe.  However, the situation is different if you are having sushi, game, or home-grown meat, milk fresh out of the neighbor’s cow, veggies from the village garden.  You are also at risk of getting infected with parasites if you are a lover of outdoor summer swimming or wading in rivers or lakes.

The reasons preventing health organizations from solving the problem of parasites once and for all are diverse enough.  The major ones are connected with the fact that despite the monitoring of rivers, dams, and lakes, as a whole the concentration of larvae or cysts in water bodies is relatively low. It takes a single cyst or larva per one cubic meter of water to get infected, yet this is so hard to detect.  Same holds true for cysts/larvae in meat or in vegetables.  Microbiological tests of food products are done with small samples.  It is not possible to test them all.  Prevention techniques for ensuring meat and vegetables are safe parasite-wise seldom work with respect to cysts and larvae.  The latter are usually protected by a cuticular envelope and they do not interact with the surroundings until a suitable host comes along.  The medical products given to livestock are efficient against the parasites in the animal but not against their cysts/larvae.  Often parasites lay their cysts/larvae in places that are not ideal for the parasite to develop.  Also, many parasites use interim hosts, such as birds, rodents, insects, amphibians, for the hatching of the cysts/larvae (Leucochloridium paradoxum, Dicrocoelium dendriticum, the Filariidae family and many other).  Last but not least, even if we wash well the food, the likelihood that we also wash away all cysts/larvae that may be there, is negligible.  Thermal processing of food guarantees food free from parasites.

The grim statistics I mentioned earlier is true for Europe too.  According to the World Health Organization, Europe has successfully managed to eliminate some exotic disease caused by parasites (e.g. malaria, Dengue fever, and to some extent Leishmaniasis, but at the same time on average seven of ten Europeans are infected with parasites.  The numbers are far more comforting for Europeans residing in places where summers tend to be shorter and cooler.  The population of Finland, the Northern parts of European Russia, Sweden, Norway, Northern Poland, Estonia, Latvia and Denmark is much luckier, with four out of ten people having parasites.  Conversely, the more to the South we go, the larger the incidence rate of parasites in humans.  Even for the exotic conditions we mentioned above such as Dengue fever, Leishmaniasis and malaria.

When we are talking about parasites, we cannot do without some scientific terms.  The sheer diversity of those organisms warrants a more steadfast approach.   The general knowledge on the topic seldom goes beyond some smattering knowledge of large round worms of humans, most adults thinking that those parasites are somehow confined to the said age group only.  This cannot be farther from the truth.  Also the parasites that we can keep in our bodies are between tens and hundreds of species (depending on where we live and on our lifestyles), and we should not be so careless as to dismiss the gaps in our knowledge about them.  Experts in taxonometrics have assiduously assigned fancy names to almost all parasites known to humans.  In the article below I will try to summarize by species the parasites that affect humans and at the same time that we have successfully treated among our patients.

There are four big groups of parasites attacking our body.

The first type are unicellular parasites called also Protozoa ( ”the simplest animals”).

This groups encompasses eukaryotic (having a nucleus) unicellular organisms.  Probably these are the first living and moving cells feeding on other cells, reproducing and surviving in most diverse conditions.  In taxonomical terms, these organisms do not belong to the kingdom Animalia, but in a stand-alone kingdom Protozoa, Protista. Here we have seven big groups: Amoebozoa, Euglenozoa, Choanozoa, Loukozoa, Percolozoa, Microsporidia and Sulcozoa.

Their feeding patterns are versatile: some have symbiotic interactions with other organisms, others are parasites and readily feed off living cells as predators.

When active they are tropozoids that move around, feed, and reproduce; some can go into an inactive from as cysts able to spawn a new host of tropozoids.

Their motility comes about in several distinct ways that divide them as follows:

  • Ameboids – moving by means of fluxing plasma into pseudopods (false feet), e.g. Entamoeba histolytica

  • Ciliates, e.g. Balantidium coli

  • Sporozoa, e.g. Plasmodium causing malaria.

They reproduce by dividing (asexually) and sexually (by merging of nuclei), while some can transfer genetic material by means of a process called conjugation.

More than twenty thousand types of protozoic microorganisms have been described.  Only a fraction of those are pathogenic for humans, yet the damages they inflict are immeasurable.  It suffices to mention malaria, along with amebiasis, Giardiasis (beaver fever), toxoplasmosis, Cryptosporidiosis, Trichomoniasis, Chagas disease, Leishmaniasis, sleeping sickness and many others.

Infection can take place in different ways: directly – through immediate contact, by fecal-oral route, vector-transmitted by agents such as insects, or by ingesting the meat of an infected animal.

Protozoic parasites are the most dangerous type for humans and are associated with highest mortality.  For ages humans have been plagued by these diseases and have been struggling to keep those infections in check.

No vaccines are available against them to date.

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