Soil-transmitted helminthiasis

Soil-transmitted helminths are essentially intestinal parasites and their eggs which are liberated along with the faeces of infected persons into the soil. Ascaris and hookworm eggs become infective as they develop into larvae in soil. Infection occurs when vegetables and fruits contaminated with egg-infested soil are consumed, or when contaminated hands or fingers are placed in the mouth. On the other hand, hookworm eggs are not directly infective. They hatch in soil, releasing mobile larvae that can penetrate the skin. Thus infection is acquired through accidental contact with contaminated soil. ==Signs and symptoms==

Symptoms become evident only when the intensity of infection is relatively high. Thus the degree of negative outcomes is directly related to worm burden; more worms means greater severity of disease. General Most conditions of STH have a light worm burden and usually have no discernible symptoms. Heavy infections however cause a range of health problems, including abdominal pain, diarrhoea, blood and protein loss, rectal prolapse, and physical and mental retardation. Severe ascariasis is typically a pneumonia, as the larvae invade lungs, producing fever, cough and dyspnoea during early stage of infection. Hookworm infections insinuate a skin reaction (dermatitis), increased white blood cells (eosinophils), a pulmonary reaction (pneumonitis), and skin rash (urticarial). Iron deficiency anaemia due to blood loss is a common symptom. Malnutrition STH is often associated with malnutrition in children as it worsens their nutritional status in multiple ways. The worms can induce intestinal bleeding, competition for nutrients (malabsorption of nutrients), frequent anaemia and diarrhoea. Soil-transmitted helminths can also cause loss of appetite. These nutritional "knock on" effects of STH can have a significant impact on the mental and physical development of children. In endemic countries, communities remain suppressed due to malnourishment, cognitive disability, and physical weaknesses as a result of heavy infections. ==Diagnosis==

For basic diagnosis, specific helminths can be generally identified from the faeces, and their eggs are microscopically examined and enumerated using fecal egg count method. However, there are certain limitations such as the inability to identify mixed infections, and on clinical practice, the technique is inaccurate and unreliable. A novel effective method for egg analysis is the Kato–Katz technique. It is a highly accurate and rapid method for A. lumbricoides and T. trichiura; however not so much for hookworm, which could be due to fast degeneration of the rather delicate hookworm eggs. ==Prevention==

Prevention and control measures to prevent soil-transmitted helminthiasis are the following: availability of clean water for personal and domestic uses, improved access to sanitation which includes the use of properly functioning and clean toilets by all community members, education on personal hygiene such as hand washing and hygienic and safe food preparation; eliminating the use of untreated human faeces as fertilizer. ==Treatment==

The World Health Organizations recommended albendazole or mebendazole for treatment. utilizes "community diagnosis" (a survey is conducted on a population sample to decide about the need of intervention) instead of "individual diagnosis," which would be much more expensive than the treatment itself. Mass deworming allows for the treatment of large number of infected individuals at a very low cost; however, many uninfected individuals are also receiving drugs. Fortunately, this poses no risk to them since the deworming medicines are extremely safe. Some researchers argue that mass deworming, in the absence of a positive test, does not improve nutrition, hemoglobin levels, school attendance, or academic performance. However, these results are derived from measuring mean improvements in the population receiving the intervention, which includes both infected and uninfected individuals. Obviously, no improvement should be expected in non-infected individuals that are treated only for logistic reasons. When health improvements are measured specifically in infected children, who are the targets of the intervention, the results indicate significant health benefits. The World Health Organization recommends mass treatments to all at-risk groups in endemic communities, especially women of childbearing age, and children. Mass treatments can also be provided to pregnant women in their second and third trimesters, and breastfeeding women. Every year over 400 million individuals are treated with this approach. For this purpose, broad-spectrum benzimidazoles such as mebendazole and albendazole are the drugs of choice recommended by WHO. These anthelminthics are safe, inexpensive, and effective for several months. Mebendazole is given twice a day for three consecutive days, while albendazole is given as a single dose. WHO recommends annual treatment in areas where between 20 and 50% of people are infected, and a twice-a-year treatment if it is over 50%; and in low-risk situations (i.e. less than 20% prevalence) case-by-case treatment. In addition to these, pyrantel pamoate is also equally effective on Ascaris. However, it has been reported that albendazole, mebendazole, and pyrantel pamoate are not entirely effective against T. trichiura with single oral doses in population-based control. Drugs for those with other diseases In cases of coinfection, combination therapy with ivermectin and diethylcarbamazine is advocated. However coinfection with malaria and HIV, especially among African women, does not respond well to the current combination therapies. It is more pressing for trichuriasis that the recommended drugs fail to provide positive results. A novel drug tribendimidine, which was approved in China by the CCDC for human use in 2004, has been subjected to clinical trials showing that they are highly effective against major human flukes, ascaris (>90% cure rate) and hookworm (>82%); however with low cure rate for whipworm (<37%). Surgical intervention In some severe cases of ascariasis, the number of Ascaris worms can cause intestinal obstruction requiring emergency surgery. ==Epidemiology==

Regions Infections are widely distributed in tropical and subtropical areas, with the greatest numbers occurring in sub-Saharan Africa, the Americas, China, and East Asia. • approximately 807–1,121 million with ascaris • approximately 576–740 million with hookworm • approximately 604–795 million with whipworm Deaths Latest estimates indicate that the total annual death toll which is directly attributable is as high as 135,000. The death toll due to the malnutrition link is likely to be much higher. == References ==