Intermediate Host: Definition, Types, & Examples

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Intermediate Host Definition

Intermediate host is a harbouring organism that provides all the hospitality services to a guest organism.

What is Intermediate Host?

The interaction between the different organisms and their association makes some of them benefitting mutually, while some parasitically and others either as competitors, commensalism or amensalism. In all these relationship, there is a host which resides within organism, providing all the nutrition and fulfilling all the requirements.

The host in commensalism, mutualism and parasitism provides 3 things to be precise, which are niche i.e habitat, nutrition and nest to lay its egg. Hosts are of 5 types and they are primary host, secondary host, paratenic host, accidental host and reservoir host. The intermediate hosts are the secondary hosts.

The intermediate host reside in the non-sexual parasite phases, whereas the primary host resides in sexual phase of the parasite. As secondary host are the intermediate host, similarly primary host are also called as definitive host.

In intermediate it’s the site for asexual reproduction of parasite, whereas in primary host it is the sexual reproduction site for parasites. In intermediate, parasite resides for a small period within the host, whereas in primary host, it stays for a longer time. Within the host, gametes combines and zygote is produced in primary host, which is not seen in intermediate host.

Examples of intermediate host are mosquitos and humans, whereas dog, humans, female anopheles mosquitos are the host in primary, whereas the parasite is plasmodium, wucheria bancrofti, lymphatic filariasis and others.

Intermediate Host and Host Parasite Coevolution

It is said that due to the pressure, they are reciprocal of each other, which is the parasite and host. In order for the host to protect itself it has evolved itself through adaptations and thus, even the parasite has made adaptations in terms of shelter, resources and others, thus such a relationship is reciprocal to each other and will always work together in unison and is called as coevolution, where the organism keeps on growing, accepting the changes and evolving with time.

Intermediate Host Examples

The very first host is the Dromedary camel and the parasite involved is MERS-CoV Virus. Another parasite is the SARS- CoV Virus and the host is masked palm civet. In this example two types of host are involved, the vertebrate the human and the invertebrate like tsetse fly, and the parasite is Trypanosoma cruzi and gambiense.

Another parasite is the Taxoplasma gondii and its host is birds and mammals. Another host are the pigs, cow and human, with its parasite the tapeworm. Liver flukes are another parasites which harbors the fish as hosts. In humans, the parasite is plasmodium. Another parasite is Dirofilaria immitis, which harbors in the mosquito like the anopheles, aedes and culex.

Intermediate Host and COVID Virus

Due to the current it’s a very vexed and a goggled topic as it has created a chaos throughout the world since 2019. Various research scientist are trying to find out the intermediate host of this virus. Since the beginning it is been said that bats are the first host of this virus, but no research or evidence has proved it and if it has begun from bat, how has it further reached to human is yet unknown.

This is an extremely controversial debate, as the intermediate host which is responsible for the spread of disease is not known and the search is going on. Since the time, there has been news stating that animals could be the reservoirs, their trading is done through complete check and under scrutiny from that period.

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