Ectoparasites

This term is generally used to refer to pathogens such as ticks, fleas, lice, parasitic flies and mites that attach or burrow into the skin and remain there for relatively long periods of time. Ectoparasites can parasitise a wide range of organisms, from humans to insects to plants.

Ectoparasites of small mammals and medium mammals are divided into two main classes which are Insecta and Arachnida. The members of the class Arachnida including order Ixodida (ticks) and Mesostigmata (mites) meanwhile class Insecta comprising Phthiraptera (lice) and Siphonaptera (fleas).

Ectoparasitoses refer to infestation with parasites that live on or in the skin. Some ectoparasites, such as many of the species of lice for example, live in continuous association with their host throughout their life-cycle and are therefore highly dependent on the host.

It can cause considerable morbidity. In many cases, infestations cause little damage to the host and do not require treatment, but in others the arthropod ectoparasite can cause serious disease, either directly by the physical damage they cause, or indirectly by transmitting microorganisms or encouraging secondary infection.

In developing countries population groups are simultaneously infested with several ectoparasite species, the parasite burden and risk of reinfestation are high, and compliance for prolonged and/or repeated treatment is poor.
Ectoparasites

Parasitic infections

Parasites use the bodies of other organisms to live and reproduce. Parasites include worms (helminths) and some single-celled organisms (protozoa).

Parasitic infections often cause intestinal illness, with symptoms like diarrhea and vomiting. But they can also give itchy skin rashes or infect other parts of human body, like brain or lungs.

There are three main classes of parasites that can cause disease in humans: protozoa, helminths, and ectoparasites. Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure and carry out complex metabolic activities. Some protozoa have structures for propulsion or other types of movement.

The helminths are worm-like parasites. The clinically relevant groups are separated according to their general external shape and the host organ they inhabit. There are both hermaphroditic and bisexual species.

While ectoparasite is generally used more narrowly to refer to pathogens such as ticks, fleas, lice, parasitic flies and mites that attach or burrow into the skin and remain there for relatively long periods of time.

Parasitic organisms are the causative agents of some of the world’s most devastating and prevalent infections. This group of pathogens includes members such as the protozoans Trypanosoma (Chagas disease and African sleeping sickness), Leishmania (leishmaniasis), Plasmodium (malaria), and the helminths such as Schistosoma (schistosomiasis), Wuchereria (filariasis), and Echinococcus (echinococcosis), among others.

Some parasitic infections, like pinworms, are common all over the world. Many other parasitic infections are more common in rural areas of the world without developed sanitation systems. People who are at higher risk for parasitic infections include:
*Young children and their parents or caregivers.
*People with compromised immune systems.
Parasitic infections

History of filariasis

Lymphatic filariasis is a neglected tropical disease caused by infection with the mosquito-borne, thread-like, parasitic filarial worms Wuchereria bancrofti, Brugia malayi and B. timori.

In Egypt, nocturnally periodic bancroftian filariasis has been endemic since Pharaonic times. The first written documents of filariasis come from the ancient Greek and Roman writers who could differentiate between the similar symptoms of leprosy and filariasis.

Jan Huygen Linschoten during his trip to Goa between 1588 and 1592 first documented the disease symptoms and wrote that inhabitants ‘‘all born with one of their legs and one foot from the knee downwards as thick as an elephant’s leg.’’

Filariasis was the first human disease described in which transmission through the skin was cause by the bites of arthropods. Doctor O. Wucherer (1868) found the embryonic filarial worms in the urine of a patient in Bahia, Brazil. T. R. Lewis (1872), working in India, observed the embryos in the urine and also in the blood, and Joseph Bancroft (1878) in Brisbane, Australia first described the adult worm. The parasite has been designated Wuchereria bancrofti.

The momentous discovery of the role of the mosquito in transmitting the disease was made by the Scotsman Patrick Mansion (1877) while he was practicing medicine in the Far East with the Chinese Imperial Maritime Customs. He became interested in the disease that confronted him, including filariasis. In that disease he recognized the parasites in peripheral blood films and also in postmortems material.

Patrick Mansion noted the nocturnal appearance of the parasites in the peripheral blood and postulated that a blood sucking insect might be responsible for transmitting the infection. Manson proved the presence of the microfilaria in the mosquito Culex fatigans, thus supplying the missing link in the life cycle of the disease.
History of filariasis

What infections can protozoa cause?

On a global basis, billions of people are infected by protozoan parasites toll due to protozoan infections is correspondingly huge.

Among the most widespread protozoan infections caused by pathogenic protozoan are as follows:
*Amoebiasis
*Giardiasis
*African Sleeping Sickness
*Leishmaniasis
*Toxoplasmosis
*Malaria
*Babesiosis
*Trichomoniasis

Plasmodium falciparum

Most intestinal protozoan infections can cause acute or chronic diarrhea in healthy individuals and may result in intractable, life-threatening illness in patients in immunosuppressive status.

All types of protozoa are single-cell organisms that can adapt to various conditions. They are much more versatile than bacteria. Protozoa are typical parasites that occupy host cells, multiply in them and then destroy them.
What infections can protozoa cause?

Lymphatic filariasis

Lymphatic filariasis is a disease that occurs mainly in tropical countries of the world, from about 41 ° N to 37 ° S. It is caused by long, slender worms of the phylum Nematoda, superfamily Filarioidea.

Lymphatic filariasis in human is caused by the developing and adults forms of filarial parasites present in the lymphatic system.

Three parasites belonging to two genera are responsible: Wucheria bancrofti, Brugia malayi and Brugia timori.

The disease is variably characterized by acute lymphatic inflammation or chronic lymphatic obstruction associated with intermittent fevers or recurrent episodes of dyspnea and bronchospasm.

It is a progressive disease leading to non-pitting edema and brawny changes that may involve a whole limb. Overtime, there is progressive enlargement, coarsening and fissuring of the skin leading to the classical appearances of elephantiasis. The limbs or scrotum may become hugely swollen. Eventually, the adult worms will doe, but the lymphatic obstruction remains and tissue damage continues.
Lymphatic filariasis

Parasites as pathogens

Parasites as pathogens
The true definition of a parasite is an organism that lives on or in another organisms, deriving benefit from it but providing nothing in return.

Nor all ‘parasites’ cause disease; organisms such as Entamoeba dispar, a protozoan, live in the human gut without causing disease and are thus colonizers.

Around 500 million individuals in the world are infected with amebiasis caused primarily (90%) by E. dispar.

This closely related species E. histolytica is capable of invading the bowel wall, causing colitis and abscesses in the liver, brain and other tissues.

E. histolytica is a powerful pathogen that uses proteases to destroy hosts’ tissues, kill some hosts’ cells and “phagocyte” red cells.

Multicellular parasites such as schistosomes may also be pathogens. In the past, diseases caused by metazoan parasites, such as schistosomiasis, were sometimes called infestations. Nowadays all parasitic diseases are called infection.
Parasites as pathogens

Genome of Highly Infectious Parasite, Giardia Lamblia Unlocked

Genome of Highly Infectious Parasite, Giardia Lamblia Unlocked
Giardia lamblia, one of the most common human parasites in the United States, causes more than 20,000 intestinal infections a year, often through contact with contaminated drinking or swimming water. In the September 28 issue of Science, an international team led by researchers at the MBL (Marine Biological Laboratory) describes the complete genome (genetic sequence) of Giardia, which could lead to the development of new drugs to combat this persistent infection, called giardiasis.

Even though there are treatments now available, a number of people get chronic giardiasis, which is difficult to eliminate. So there is interest in new treatments. The Giardia parasite lives in the human intestine in a swimming and feeding form called a trophozoite, which is eventually expelled through the stools. Outside the body, Giardia takes the form of a highly infectious cyst that can live for weeks in water, soil, food, or on other surfaces.

Giardiasis is most common among children, especially those who are exposed to diaper changing. Swimmers, hikers, campers and others who drink untreated water are also prone to the infection (hence the nickname "backpacker's disease" or "beaver fever"), as are international travelers. Common symptoms include diarrhea, nausea, stomach cramps and gas, and usually persist two to six weeks. Because the parasite clings to intestinal cells that absorb fats and nutrients, giardiasis can lead to severe complications such as poor nutrient absorption and weight loss.

Although not life threatening, Giardia is a rather fastidious parasite and quite important from an economical viewpoint worldwide and in the United States, where it constitutes a major cause of diarrheal disease in children in daycare centers. Analysis of the Giardia genome revealed several unusual proteins that are promising drug targets. Drugs can be devised that will interfere with the parasite's ability to replicate, or to move or bind in the small intestine, or to exist at all.

The MBL team also investigated the evolutionary history of this ancient parasite. Giardia is a single-celled eukaryote, meaning its cell has a nucleus, as do the cells of humans and most other multicellular organisms. But the Giardia genome is compact compared to other eukaryotes, with simplified machinery for several basic processes, such as DNA replication and RNA processing. If the Giardia genome had originally been complex and experienced gene loss over evolutionary time, Morrison says, one would expect to see parts of the machinery intact and parts missing. This, however, wasn't the case.
Researchers embarked upon this genome project because of its importance to human health and suggestions from earlier molecular analyses that Giardia represents a very early-diverging lineage in the evolutionary history of eukaryotes. Giardia's genome content and architecture support these theories about the parasite's ancestral character.

Another important finding is that the genes that allow Giardia to evade the human immune response are organized differently than in other parasites. In the host intestine, Giardia eludes an immune system attack by shifting the proteins it displays on its surfaces. The genes for these surface proteins are scattered throughout the Giardia genome rather than found in clusters, as in other parasites.
Genome of Highly Infectious Parasite, Giardia Lamblia Unlocked
Extract from: http://www.medicalnewstoday.com