Hookworm is a helminthic invasion caused by parasitization in the human intestine of roundworms (hookworms or necators) belonging to the Ancylostomatidae family. Clinically, hookworm is manifested by papulo-vesicular rash, cough, shortness of breath, impaired appetite, nausea, abdominal pain, diarrhea, iron deficiency anemia. The diagnosis of hookworm is confirmed by the detection of helminth eggs in faeces and duodenal contents. Treatment consists in carrying out deworming and correction of anemia, followed by a three-time control examination of feces.
B76 Hookworm disease
Hookworm – helminthiasis (hookworm and necatosis) caused by parasitic roundworms – hookworms. Hookworm and necatosis are combined into one group based on the biological similarity of pathogens, their frequent joint parasitization in the body, as well as the similarity of clinical and epidemiological signs of invasion. Both helminthiasis in the early stages occur with allergic lesions of the skin and respiratory tract, and in the later stages – with impaired gastrointestinal function and the development of iron deficiency anemia. Hookworm diseases are common parasitic diseases that affect 25% of the world’s population, mainly in regions with a low level of sanitary culture. In terms of the frequency of infection, hookworm infections are second only to enterobiosis and ascariasis.
Causes and ways of infection
The pathogens of hookworm (hookworm – Ancylostoma duodenale) and necatorosis (Necator – Necator amencanus) belong to a single family Ancylostomatidae. They are united by a common morphology, development cycles and the effect exerted on the host organism. Both types of helminths belong to the class of roundworms (nematodes) and by the nature of their development belong to geohelminths.
Hookworm pathogens have a pinkish-yellowish color and small size: female hookworms are 10-13 mm long, males are 8-10 mm; necatora are 9-10 mm and 5-8 mm, respectively. At the head end of the individuals there is an oral capsule, with which the parasites attach to the wall of the small intestine. The oral sucker of the hookworm has 2 dorsal and 4 ventral cutting teeth, the necator has 2 cutting chitin plates.
Hookworm eggs have the same structure: oval shape, smooth colorless shell, dimensions 66×38 microns. Each egg contains 4-8 blastomeres. The life cycle of hookworm pathogens begins with the ingress of helminth eggs with feces into the external environment. The development of larvae occurs in the soil at a temperature of 14-40 ° C and humidity above 80%. After two molts, after about 7-10 days, hookworm larvae become invasive.
Infection of a person with hookworm can occur by two mechanisms – fecal-oral and percutaneous (percutaneous); by water, food or contact routes. In the first case, the larvae enter the host’s body through the mouth when eating seeded water, vegetables or fruits. The percutaneous path of infection involves the active penetration of invasive larvae through the skin when a person comes into contact with contaminated soil (while walking barefoot, lying on the ground, performing excavation and agricultural work). Having penetrated through the skin barrier, the larvae enter the bloodstream, then migrate to the right parts of the heart and lungs, from where they penetrate the pharynx through the respiratory tract and are swallowed a second time. Once in the small intestine, after 5-6 weeks, the larvae turn into sexually mature helminths capable of laying eggs on their own. With oral hookworm infection, there is no migration stage – the larvae immediately end up in the small intestine. The life cycle of hookworms is 7-8 years, necators – up to 15 years. Risk groups susceptible to hookworm infection include agricultural workers, miners, summer residents, and children.
During ankylostomidosis, there are 3 phases: invasive, migratory and intestinal. The first phase is associated with the introduction of larvae through the skin into the human body, which is accompanied by a clinic of dermatitis or urticaria – the appearance of a rash (erythematous, papular, vesicular), local edema, burning and itching of the skin, persisting for 10-12 days.
During the second phase of hookworm disease (migration of larvae through the host body), the body is sensitized by the products of their vital activity with the development of allergic reactions. In addition, injury to the capillaries of the pulmonary alveoli and respiratory tract tissues is clinically manifested by focal pneumonia, pleurisy, bronchitis, tracheitis, laryngitis. Patients with hookworm disease complain of cough, shortness of breath, hoarseness of voice, subfebrility.
Ankylostomidosis enters the third (intestinal) phase 30-60 days after invasion. This stage has a long, chronic course and is associated with the parasitization of hookworms in the small intestine, where they attach to the mucous membrane with the help of teeth, injuring it. Erosions and ulcers form at the site of fixation of the parasite, which can bleed for a long time, leading to the development of iron deficiency anemia. In addition, being hematophages by the method of nutrition, each individual of the necator consumes 0.03-0.05 ml of blood per day, hookworms – 0.16-0.34 ml, which also contributes to chronic blood loss. The intestinal phase of ankylostomidosis proceeds with duodenitis phenomena – impaired appetite, taste perversion, nausea, vomiting, pain in the epigastric region, diarrhea or constipation.
With a prolonged course of hookworm disease or massive invasion, children may experience a decrease in body weight, a delay in mental and physical development. Adult patients may suffer from irritability, sleep disorders, increased fatigue; women often have a violation of the menstrual cycle. The development of anemia is accompanied by weakness, dizziness, tachycardia, tinnitus.
Diagnosis and treatment
In various phases of ankylostomidosis, the patient can seek medical help from an otolaryngologist, pulmonologist, gastroenterologist or therapist. Clinical and epidemiological data are taken into account when diagnosing ankylostomidosis. Hypochromic iron deficiency anemia, increased ESR, eosinophilia, and hypoalbuminemia are noted in peripheral blood. When examining the general sputum analysis, a large number of eosinophils are detected. During the migration phase, inflammatory eosinophilic infiltrates can be detected on lung radiographs; signs of myocardiodystrophy can be detected on ECG. The radiography data of the barium passage indicate intestinal hypotension, impaired motility with the phenomena of stagnation of fecal masses.
The results of fecal analysis for helminth eggs or examination of the contents of the duodenal duodenum obtained by duodenal probing are crucial for confirming hookworm disease. In addition, serological diagnostic methods (hemagglutination and latex agglutination reactions) are used. Since hookworm eggs have the same structure, the identification of helminths (hookworms and necators) is possible only after deworming and excretion with the feces of adults. Ankylostomidosis requires differential diagnosis with other helminthiasis, as well as anemia of other etiology.
Etiotropic therapy of ankylostomidosis is carried out with anthelmintic drugs prescribed by an infectious disease specialist (parasitologist). The following drugs are used for deworming: pyrantel, befenia hydroxynaphtoate, levamizole, mebendazole. 3-4 weeks after anthelmintic therapy, the effectiveness of treatment is monitored – a 3-fold stool examination with an interval of 1 month. Symptomatic and pathogenetic treatment of hookworm disease involves the appointment of iron preparations, vitamin B12, folic acid, antihistamines, etc.
Prognosis and prevention of hookworm
In most cases, with timely diagnosis and treatment, ankylostomidoses end in complete recovery. Subsequent medical examination of patients who have had hookworm disease is carried out annually for 4 years; those who have had necatosis – for 7 years. Severe complications and lethal forms of hookworm disease develop with the advanced course of the disease.
Preventive measures consist in observing the norms of personal hygiene – washing hands after going to the toilet, protecting the skin in contact with the ground, careful processing of fruits and vegetables, boiling water before use, etc. Sanitary treatment of soil areas and environmental objects, presumably contaminated with hookworm larvae, is of great importance. High-risk groups for the incidence of hookworm should undergo an annual medical examination.