Hookworm infection.txt

Hookworm infection

Signs and symptoms
No symptoms or signs are specific for hookworm infection, but they give rise to a combination of intestinal inflammation and progressive iron-deficiency anemia and protein deficiency. Coughing, chest pain, wheezing, and fever sometimes result from severe infection. Epigastric pains, indigestion, nausea, vomiting, constipation, and diarrhea can occur early or in later stages, as well, although gastrointestinal symptoms tend to improve with time. Signs of advanced severe infection are those of anemia and protein deficiency, including emaciation, cardiac failure, and abdominal distension with ascites.
Larval invasion of the skin (mostly in the Americas) can produce a skin disease called cutaneous larva migrans also known as creeping eruption. The hosts of these worms are not human and the larvae can only penetrate the upper five layers of the skin, where they give rise to intense, local itching, usually on the foot or lower leg, known as ground itch. This infection is due to larvae from the A. braziliense hookworm. The larvae migrate in tortuous tunnels between the stratum basale and stratum corneum of the skin, causing serpiginous vesicular lesions. With advancing movement of the larvae, the rear portions of the lesions become dry and crusty. The lesions are typically intensely itchy.
Incubation period
The incubation period can vary between a few weeks to many months, and is largely dependent on the number of hookworm parasites an individual is infected with.

Diagnosis
Diagnosis depends on finding characteristic worm eggs on microscopic examination of the stools, although this is not possible in early infection. Early signs of infection in most dogs include limbular limping and anal itching. The eggs are oval or elliptical, measuring 60 by 40 µm, colorless, not bile stained and with a thin transparent hyaline shell membrane. When released by the worm in the intestine, the egg contains an unsegmented ovum. During its passage down the intestine, the ovum develops and thus the eggs passed in feces have a segmented ovum, usually with 4 to 8 blastomeres.
As the eggs of both Ancylostoma and Necator (and most other hookworm species) are indistinguishable, to identify the genus, they must be cultured in the lab to allow larvae to hatch out. If the fecal sample is left for a day or more under tropical conditions, the larvae will have hatched out, so eggs might no longer be evident. In such a case, it is essential to distinguish hookworms from Strongyloides larvae, as infection with the latter has more serious implications and requires different management. The larvae of the two hookworm species can also be distinguished microscopically, although this would not be done routinely, but usually for research purposes. Adult worms are rarely seen (except via endoscopy, surgery or autopsy), but if found, would allow definitive identification of the species. Classification can be performed based on the length of the buccal cavity, the space between the oral opening and the esophagus: hookworm rhabditoform larvae have long buccal cavities whereas Strongyloides rhabditoform larvae have short buccal cavities.
Recent research has focused on the development of DNA-based tools for diagnosis of infection, specific identification of hookworm, and analysis of genetic variability within hookworm populations. Because hookworm eggs are often indistinguishable from other parasitic eggs, PCR assays could serve as a molecular approach for accurate diagnosis of hookworm in the feces.

Treatment
Anthelmintic drugs
The most common treatment for hookworm are benzimidazoles, specifically albendazole and mebendazole. BZAs kill adult worms by binding to the nematode's β-tubulin and subsequently inhibiting microtubule polymerization within the parasite. In certain circumstances, levamisole and pyrantel pamoate may be used. A 2008 review found that the efficacy of single-dose treatments for hookworm infections were as follows: 72% for albendazole, 15% for mebendazole, and 31% for pyrantel pamoate. This substantiates prior claims that albendazole is much more effective than mebendazole for hookworm infections. Also of note is that the World Health Organization does recommend anthelmintic treatment in pregnant women after the first trimester. It is also recommended that if the patient also has anemia that ferrous sulfate (200 mg) be administered three times daily at the same time as anthelmintic treatment; this should be continued until hemoglobin values return to normal which could take up to 3 months.
Hookworm infection can be treated with local cryotherapy when the hookworm is still in the skin.
Albendazole is effective both in the intestinal stage and during the stage the parasite is still migrating under the skin.
In case of anemia, iron supplementation can cause relief symptoms of iron deficiency anemia. However, as red blood cell levels are restored, shortage of other essentials such as folic acid or vitamin B12 may develop, so these might also be supplemented.
During the 1910s, common treatments for hookworm included thymol, 2-naphthol, chloroform, gasoline, and eucalyptus oil. By the 1940s, the treatment of choice used tetrachloroethylene, given as 3 to 4 cc in the fasting state, followed by 30 to 45 g of sodium sulfate. Tetrachloroethylene was reported to have a cure rate of 80 percent for Necator infections, but 25 percent in Ancylostoma infections, and often produced mild intoxication in the patient.
Reinfection and drug resistance
Other important issues related to the treatment of hookworm are reinfection and drug resistance. It has been shown that reinfection after treatment can be extremely high. Some studies even show that 80% of pretreatment hookworm infection rates can be seen in treated communities within 30–36 months. While reinfection may occur, it is still recommended that regular treatments be conducted as it will minimize the occurrence of chronic outcomes. There are also increasing concerns about the issue of drug resistance. Drug resistance has appeared in front-line anthelmintics used for livestock nematodes. Generally human nematodes are less likely to develop resistance due to longer reproducing times, less frequent treatment, and more targeted treatment. Nonetheless, the global community must be careful to maintain the effectiveness of current anthelmintic as no new anthelmintic drugs are in the late-stage development.

Treatments
Treatment in the early 20th century relied on the use of Epsom salt to reduce protective mucus, followed by thymol to kill the worms. By the 1940s, tetrachloroethylene was the leading method. It was not until later in the mid-20th century when new organic drug compounds were developed.