Arthropods are the most important group of organism on planet earth both in terms of abundance and number of species. They pose various problems to humans. The most common problem associated with arthropods are annoyance (or nuisance), allergic reactions, envenomation, allergic reactions, invasion of host tissues (myasis) and diseases transmission.
Annoyance or nuisance
Certain arthropods irrespective of their capacity to bite or transmit disease can cause nuisance to human and other animals. Some insects such as lice, bed bugs do not transmit diseases to human, but their bite can cause inflammation to thee skin of their hosts. Other arthropods that do not bite may become annoying because of their abundance and small number. They are usually attracted to human and animal eyes and noses to whom they cause significant annoyance. This is typically the case of midges and eye gnats that are preferentially attracted to human and animal eyes. Among annoying arthropods, we can also list common houseflies and cockroach which do not vector any disease to human but can become annoying if they reach a large number in human habitations. Annoyance arthropods often attack human while they are camping outdoors.
List of Arthropods That Cause Annoyance
- Bed bugs
- Deer flies
- Horse flies
- Tsetse flies
- Stable flies
- Black flies
- Biting midges
- Sand flies
Envenomation consists to the injection of venom through the skin of the host. There are various groups of arthropods that inject venom when biting or sting their hosts. The most well known insect that inject venom are bees, wasps, ants, spiders and scorpions. The venom of these insects may cause inflammation and allergic reaction. Some scorpions venom may be fatal to humans (reference). Other arthropods such as the blister beetle and some caterpillars produce toxins that can cause problems to humans and other animals when ingested or contact is made to the skin. In most cases envenomation result inflammatory response through the skin with itching or temporary pain. These reactions vary depending on the type of venom and the inflammatory response of the person or animal stung. Blister beetle toxin, when ingested by animal can cause systemic reaction that can be life threatening.
Certain arthropods cause allergic reactions in human and animals they come into contact. Most arthropods species that cause envenomation also induce allergic reactions in their victims. The spectrum of the reaction may vary according to individual response and the degree to which their immune system respond. Allergic reactions in humans have been documented following the bite of wasp, bee, ants, fleas, mosquitoes, bed bugs, lice and chiggers. Toxin-producing beetles and caterpillars can also cause allergic reactions in humans and animals. When large population of cockroach become establish their odors can also induce allergic reaction in humans and people may develop certain respiratory conditions. Repeated exposure to certain arthropods allergens can result in two different scenario:
- The subject may become desensitized to the bite or sting f the arthropods due to repeated exposure. This has been observed with people become insensitive to bee sting after certain number of exposure.
- Hyper allergenicty b leading to anaphylactic chocs with life threatening consequences in some cases.
Invasion of Host Tissues or Myasis
‘The interaction of some arthropods with humans and animals result in the invasion of host tissue. Depending on the severity of the case, this interaction can vary from subcutaneous invasion to full organ invasion. In most cases it is immature stages of parasitic arthropods that invade host tissues. The most widespread of host tissue invasion is caused by fly larvae and the phenomenon is known as myasis. The most common organs that are invaded by arthropods include lungs and intestines. Certain mites species are also known to invade dermal glands and nasal openings.
Arthropods transmit a wide variety of pathogenic organisms including viruses, bacteria, protozoans and nematodes. There are two main ways that do so including, biologically and mechanically. Biological Transmission involve the development and/or reproduction of the pathogen inside the body of the arthropod vector. For instance, plasmodium, protozoan responsible for malaria must undergo developmental change inside their mosquito host before being transmitted to humans. Other vector-borne diseases such as African trypanosomiasis, chagas disease, filariasis and leishmaniasis involve biological transmission. Mosquitoes and ticks are by far the most important vectors of human and animal diseases. The most devastating mosquito-borne disease is malaria that is prevalent mainly in Africa and other developing countries. In mechanical transmission, the pathogen is passed to their human or animal hosts through the insect mouthparts and appendages (such as legs). In some cases infection occur through regurgitation of infected blood meal. Some arthropods are ectoparasites and live on their hosts. The are 8 orders of insects that are often associated with disease transmission. These orders includes:
- Blattodea (cockroaches),
- Phthiraptera (lice),
- Hemiptera (bed bug, kissing bugs, assasing bugs)
- Coleoptera (beetles)
- Siphonoptera (fleas)
- Diptera (mosquitoes, flies, midges,)
- Lepidoptera (Moths and butterflies)
- Hymenoptera (wasps, ants, bees, hornets)
Arthropods groups other than insects are also of medical importance. Such arthropods include: