Loa loa filariasis : Also known as loaisis, this is caused by the Loa loa worm, or African eye worm. It causes itchy swellings on the body. It occurs mainly in Central and West Africa and is transmitted through deerfly bites. Mansonellosis : This is passed on through the bites of midges or blackflies. It affects the layers under the surface of the skin, but it can enter the blood. It can lead to angioedema , swellings, skin rash, fever, and joint problems. It is present in Africa and Cental America.
River blindness : Caused by a worm known as Onchocerca volvulus , this affects the eyes , skin, and other body tissues. It is found near fast flowing water. It is transmitted through the bite of a blackfly. It occurs in South America, but 90 percent of cases are in Africa. Lung fluke : Also known as paragonimiasis, this affects the lungs , causing symptoms similar to those of tuberculosis TB. However, it can reach the central nervous system, leading to meningitis.
It is transmitted when eating undercooked or raw freshwater crabs , crayfishes, and other crustaceans. It is most common in parts of Asia. Schistosomiasis, bilharzia, or snail fever : There are different types of schistosomiasis. They can affect the skin and internal organs. It results from exposure to fresh water that has snails in it that are infected with the blood fluke, or trematode worm.
The worms are not found in the U. Sparganosis : Humans can become infected if they eat foods tainted with dog or cat feces that contains the larvae of a tapeworm of the Spirometra family. It can lead to a migrating abscess under the skin.
It is rare. Strongyloidiasis : This can lead to severe and possibly fatal immunodeficiency. The parasite penetrates through the skin and affects the lungs, skin, and intestines. It is passed on through direct contact with contaminated soil.
It most occurs in tropical and subtropical regions. Beef and pork tapeworms : Taeniasis is caused by tapeworms of the taenia family. They affect the intestines.
They are passed on by eating undercooked beef or pork. Toxocariasis : A roundworm transmits this infection from animals to humans. It affects the eyes, brain, and liver. It is caused by accidentally swallowing the eggs of the parasite, for example, when young children play with soil. Nearly 14 percent of people in the U. Most never have symptoms. Trichinosis : This is caused by the roundworm of the Trichinella family. Infection can lead to intestinal symptoms, fever, and muscle aches. It is passed on by eating undercooked meat.
Whipworm : Also known as trichuriasis , whipworms live in the large intestine. Eggs are passed in feces. It is common all over the world.
Humans can become infected when ingesting the eggs, for example on unwashed fruit or vegetables. Elephantiasis lymphatic filariasis : This is transmitted through mosquito bites.
The adult worms live in the lymph system. Infection can lead to lyphedema and elephantiasis, in which swelling can cause disfigurement and disability. In the Americas, it is passed on by the Culex quinquefasciatus mosquito. Ringworm is sometimes mistaken for a worm, but it is not a worm. It is a fungal infection. Bedbug : These can affect the skin and vision. They are found all over the world. Sharing clothing and bedding can spread infection. They may be present in newly rented accommodation and hotel rooms.
Body lice : These are common worldwide. Infection can spread through sexual activity, skin-to-skin contact, and sharing bedding or clothing. Crab lice : These affect the pubic area and eyelashes. They are common all over the world and spread through sexual activity, skin-to-skin contact, and sharing bedding or clothing. Demodex : These affect the eyebrow and eyelashes. They are common all over the world and can spread through prolonged skin contact. Scabies : This affects the skin.
It is common all over the world and can spread through sexual activity, skin-to-skin contact, and sharing bedding or clothing. Screwworm : This is transmitted by a fly, and it affects skin and wounds.
It is found in Central America and North Africa. Head lice : These live on the scalp and affect the hair follicles. They are common all over the world and spread through head-to-head contact. A reaction to their saliva causes itching. Parasites come in many shapes and sizes and can lead to a wide variety of symptoms and health issues. Some parasites are treatable and others are not. Lymphedema is a long-term condition in which fluid collects in tissues, causing swelling.
Lymphedema most commonly affects one or both of the arms or…. Bedbugs are small wingless insects that feed exclusively on the blood of warm-blooded animals. They need to feed regularly to reproduce, lay eggs, and…. Trichomoniasis is a common sexually transmitted infection.
There are often no symptoms, but it can lead to complications. It is treatable with…. The tapeworm is a parasite that lives in the gut. Parasitic organisms are found almost everywhere, from tropical and sub-tropical regions to freezing places like Antarctica. Yet, what every parasite needs is an organism that provides food, shelter, and a place to reproduce. This organism is called a host. The host is eventually harmed by its interaction with the parasite.
Parasites can be classified into two groups, depending on where they live in their hosts. Parasites that live outside the host are called ectoparasites Figure 2A.
For example, a flea is a parasite that lives on cats. In contrast, parasites that live inside their hosts are known as endoparasites Figure 2B. For instance, Wuchereria bancrofti is a worm that lives in the human lymphatic system and causes a disease known as elephantiasis.
Among the endoparasites, some can live inside the host cells and are called intracellular parasites. Plasmodium falciparum is one such parasite, because it lives and grows inside the red blood cells of people who have malaria.
Parasites also vary in the number of hosts they need to survive. While certain parasites need only one host, other parasites use multiple hosts to complete their life cycles. The host in which the parasite completes its sexual reproduction is called the definitive host.
Parasitism is a constant battle for survival between the parasite and its host. Because parasites depend on their host for food and shelter, they must not destroy the host until they are ready to move on to the next host.
Meanwhile, the hosts must protect themselves from harm. To protect themselves, the hosts constantly challenge parasitic organisms by creating unfavorable conditions. The host will try to deprive the parasites of nutrients, effectively starving them, or will attack the parasites with its strong immune defenses.
To live in such a difficult environment, each parasite has evolved different survival strategies. Over millions of years of evolution, parasites have acquired lots of interesting features to help them adapt to specific environments [ 1 ]. Here are some of them.
There are a number of parasites that cause diseases in humans. Parasitic diseases are most common in developing countries in tropical and sub-tropical regions of the world Figure 3. These places are often hot and humid, conditions which are suitable for the growth of many parasites.
In addition, tropical countries are often affected by poverty, poor sanitation, inadequate healthcare facilities, and low educational level. These factors often increase the transmission of parasitic diseases through insects, contaminated water, or contaminated soil, and make it difficult to control or eliminate them.
Below, we describe some important parasitic diseases in tropical regions Table 1. Malaria is one of the most common diseases in Africa and other tropical places, where it causes millions of deaths every year. The female Anopheles mosquito transmits the parasite when it draws blood from a human. Food and water-borne outbreaks of these protozoan parasites have occurred, and the infectious cyst form of the parasites is relatively resistant to chlorine Other species of protozoan parasites can also be found in the human gut, but they are not pathogenic, except Microsporidia sp.
In an article published in this issue of the Journal, Jacobsen et al. They have found a high prevalence of intestinal parasites, especially the intestinal protozoan parasites.
They have used the traditional microscopic technique to diagnose intestinal parasitic infections. In total, stool samples were examined from children aged months and found that The overall prevalence of intestinal protozoan parasites were: E. A recent study in Nicaragua in asymptomatic individuals found that This study proves again that the diagnosis of E. To understand the real prevalence of E. Over the last several years, we have seen new approaches to the diagnosis, treatment, and prevention of intestinal protozoan parasites.
However, the diagnosis and treatment of intestinal helminth infections have not been changed much, and the traditional microscopic method can be used for their diagnosis. Antigen-detection tests are now commercially available for the diagnosis of all three major intestinal protozoan parasites. Diagnosis of E. In several studies, this E.
These studies have found that this antigen-detection test is sensitive and specific for the detection of E. In a study in Bangladesh, E. In a study in Nicaragua among patients with diarrhoea, where E. In a study conducted in a cohort of Bangladeshi children found that the prevalence of E.
No studies that have been carried till date using E. In addition to the antigen-detection test, several PCR-based tests specific for E. Rapid diagnostic test for the detection of E. Diagnosis of giardiasis is best accomplished by detection of Giardia antigen in stool, since the classic microscopic examination is less sensitive and specific. A recent comparison of nine different antigen-detection tests demonstrated that all had high sensitivity and specificity, except one Giardia -specific antigen-detection tests are now also commercially available from several diagnostic companies, and their performance is quite good, except a few.
In addition to antigen-detection tests, PCR-based test for the detection of G. The population genetics of Giardia are complex. However, a recent genetic linkage study has confirmed the distinct grouping of Giardia in two major types Differentiation of these two assemblages of G.
Findings of the largest case-control study conducted to date on the relationship between genotypes of G. This study has shown that the Giardia assemblage A infection is associated with diarrhoea.
In contrast, Giardia assemblage B infection is significantly associated with asymptomatic Giardia -associated infection, which was found to occur at a significantly higher rate The PCR-based approach allowed resolution of infection to the genotype level and brought some clarity to the findings of asymptomatic giardiasis.
Diagnosis of cryptosporidiosis is also best accomplished by detection of Cryptosporidium spp. Cryptosporidium spp. There are two main species of Cryptosporidium that infect humans: C. The PCR-based test is required for differentiation of these two species of Cryptosporidium spp. Both C. There are a few other species of Cryptosporidium that also can be found in humans 31 — Rapid diagnostic tests for the detection of G.
Multiplex PCR-based test for the detection of E. Personal communication, These modern antigen-detection tests and PCR-based tests need to be used for understanding the actual prevalence and epidemiology of these protozoan parasites. Soil-transmitted helminth infections are invariably more prevalent in the poorest sections of the populations in endemic areas of developing countries. The goal is to reduce morbidity from soil-transmitted helminth infections to such levels that these infections are no longer of public-health importance.
An additional goal is to improve the developmental, functional and intellectual capacity of affected children Highly-effective, safe single-dose drugs, such as albendazole, now available, can be dispensed through healthcare services, school health programmes, and community interventions directed at vulnerable groups As these infections are endemic in poor communities, more permanent control will only be feasible where chemotherapy is supplemented by improved water supplies and sanitation, strengthened by sanitation education.
0コメント