Introduction
Hookworm infection is one of the most common disease in Nigeria infecting people at certain period of their lifetime with far reacting disabling and debilitating effects on the individual victims and on the social economic development of the nation. The causative organism of the common hookworm infection are the Strongylid Nematodes Necator Americanus and the Ancyclostoma Duodenale (Udonsi,2007).
WHO (2007) observed that the geographical distribution of the two main hookworms N. Americanus and A. Duodunale used to be restricted and relatively distinct, the former being more prevalent in Europe and South Western Asia and the latter in tropical Africa and in the Americas. However, over the years both parasites have become widely distributed throughout the tropics and rigid demarcations are no longer tenable.
In Nigeria the presumed human hookworms N. Americanus and A. Duodenale both occur (Odubumni et al., 2007); Nwosu (2011) observed that these two diseases (Muylostomiasis and Necatoriasis) are associated with poor hygiene practices and improper disposal of human wastes. These features are typical of most rural and urban settlements in Nigeria where there is poor planning and inadequate public health facilities. Bundy et al (2009) estimated that over 900 million people are infected with hookworm disease worldwide.
Hookworm in Nigeria is markedly season because of the influence of climate on the free living larvae stages of the parasites. Nwosu and Anya (2008) suggested that this factor could be of serious economic consequences if the period of heavy infection or high incidence concedes with busy period in the agricultural communities in the country. The most serious consequence of hookworm infection is anaemia secondary to loss of iron and protein of the gut (Hotex et al., 2010) it has been estimated that a single A. Duodenale ingests about 150ɥl of blood per day while N. Americanus sucks about 30ɥl (Midze et al., 2010).
However, the blood loss through this channel cannot be visualized by the necked eyes. In a situation where the worm burden is significantly high in an individual, infection is normally severe with iron deficiency anaemia particularly in people with inadequate iron reserves or intake. In most developing countries for instance anaemia in pregnancy has been associated with worm infestation especially hookworm (Hotex, 2009).
Worldwide N. Americanus is the predominant etiology of human hookworm infection whereas, A. Duodenale is somehow restricted geographically. Most infected individuals are concentrated in Sub-Saharan, Africa and East Asia, the Pacific Islands with each region having estimates of 198 million and 149 million infected individual respectively (De-benoist et al., 2008).
Majority of these infected individuals live in poverty stricken areas with poor environmental sanitation.
Conceptual framework
Hookworm infection is an infection by a type of intestinal parasite in the round worm group. Initially, there may be itching and a rash at the site of infection. There may be no symptom in those infected by a few worms. In those infected with many worms, there may be abnormal pains, diarrhoea, weight loss and feeling tired. The mental and physical development of children may be affected anaemia may result (Adenusi and Ogunyomi, 2008)
Previous report from other parts of Nigeria (Chan et al., 2007) have shown that N. Americanus is the most common and dominant hookworm species and infections with it represent only a small proportion of the local hookworm infections over the years in order to manage this disease, there is need to access the prevalence of this parasite in Nigeria and in Ifie locality where the weather favours the development of the parasite.
Causes of hookworm infection
Parasitic roundworms or hookworms cause these infections. The two types of hookworms that causes infection are Necator Americanus and Ancylostoma Duodenale. The eggs of these hookworms end up on the ground after passing through human faeces. They hatch into larvae which stay in the soil until they have a chance to break through human skin.
Clinical symptoms
There are no specific symptoms or signs of hookworm infection but they give rise to a combination of intestinal implementation and progressive iron deficiency anaemia and protein deficiency. Coughing chest pain wheezing and fever will sometimes result from severe infection. Epigastric pains, indigestion, nausea, vomiting, constipation and diarrhoea 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 Anaemia, protein deficiency including emaciation, cardiac failure, abdominal distension with ascites.
Larvae, invasion of the skin can produce a skin disease called cutaneous larva migrans or creeping eruption. However, the host of these parasite is not human but the larvae can only penetrate the upper of the skin, where they give rise to intense local itching usually on the foot or lower leg known as ground itch. This is caused by a specie called A. Braziliense hookworm (James et al., 2008).
Morphology
- Duodenale worms are grayish white or pinkish with the head slightly bent in relation to the rest of the body. This bend forms a definitive hook shape at the anterior end for which hookworm are named. They possess well developed mouths with two pairs of teeth. While males measure approximately one centimetre by 0.5 millimetres, the females are often larger and stouter. Additionally males can be distinguished from females based on the presence of a prominent posterior corpulatory bucca (CDC, 2008).
- Americanus is very similar in morphology to A. Duodenale, but it is generally smaller with males usually 5-9mm long and females about 1cm long. Necator Americanus possesses a pair of cutting plate in the bucca capsule. Its shape however, is more defined than in Ancylostoma. (Marcell and John, 2008)
Life cycle
Both species of hookworm can be found in warm moist soil where they will eventually hatch into first stage larvae (L1). The first stage larvae is a non-infective rhabiditiform stage that feeds on soil microbes and eventually molt into second stage larvae (L2). This is also a rhabiditiform stage feeds for about 7days then molt into the 3rd stage (L3) which is the filari form stage of the parasite (non feeding infective form). This filari form are extremely motile and will seek higher ground to increase their chances of penetrating the skin of human host. The filari form can survive up to 2weeks without finding a host. While N. Americanus lervae only infect through penetration of skin, A. Duodenale can infect both through skin penetration and through oral ingestion.
After the filari form has successfully entered the host, the larvae travel through the subcutaneous venules and lymphatic vessels of the human host. Eventually filari larva enter the lungs through the pulmonary capillaries and break into the alveoli. They will then travel up the trachea to be coughed and swallowed by the host. After being swallowed, the larvae move into the small intestine where it molts into the 4th stage (L4) or adult form. The entire process from penetration to adult development takes about 5-9 weeks. The female adult worms will release 9,000,to 10,000 egg per day and A. Duodenale 25,000 -30,000 eggs per day which are passed in the faeces of the human host. These eggs will hatch in the environment within several days and the cycle will start anew (Bethony et al., 2008)
Fig. 1: Life cycle of hookworm
Pathophysiology of hookworm
Hookworm infection is generally considered to be asymptomatic, but as Norman stoll described in 1962, hookworm infection is an extremely dangerous infection because, its damage is silent and insidious. There are general symptoms that an individual may experience soon after infection. Ground itch which is an allergic reaction at the site of entry is common in patient with N. Americanus.
More so, coughing and pneumonitis may result as the larvae begins to break into the aveoli and travel up the trachea. Once the larvae reach the small intestine of the host and begin to mature, the individual will suffer diarrhoea and gastrointestinal (GIT) discomfort. Major mobility associated with hookworm infection is cause by intestinal blood lose, iron deficiency anaemia and protein malnutrition. They result mainly from adult hookworm in the small intestine ingesting blood, rupturing erythrocytes and degrading haemoglobin in the host. The long term blood loss can manifest itself physically through facial and peripheral edema, eosinophilia and pila caused by iron deficiency anaemia are also experienced (Markell and John, 2008.)
Recently it is now widely accepted that children who suffer from chronic hookworm can suffer from growth retardation as well as intellectual and cognitive impairments (Gasser et al., 2009)
Epidemiology/ prevalence
It is estimated that between 576-760 million persons are infected with hookworm (Feuwick, 2012) and about 80 million severely affected (Gasser et al., 2009). The major cause of hookworm is caused by N. Americanus found in sub–Saharan Africa and Asia (Hotex, 2009). A. Doudenale is found in more scattered local environment, Europe and Mediterranean. The most affected are found in sub-Saharan Africa, East Asia and the pacific Island with each region having estimates of 198 million and 148 million respectively. Other region affected includes, South Asia (50 million) Latin American and the Caribbean (50 million) south Asia (59 million) middle East, North Africa (10 million) (Bethony et al., 2008).
A majority of these infected individual live in poverty stricken areas with poor sanitation. In a related study in Rivers State, Nigeria, by Aba and Arene, (2015) a prevalence of 25.0% was obtained for hookworm species. It was also stated that infection was generally higher in males at (57-60%) prevalence than female at (40 -42%) prevalence. Similar study was also carried within rural communities in Abia State Nigeria by Amaechi et al, (2013). A prevalence of (5.1%) was screened for hookworm. It was also stated that males have more prevalence than females and the age range 5-7yrs also had the highest prevalence as compared to others.
The study of Olusola et al. (2011) in Osogbo Nigeria, stated a prevalence of (5.1%) of hookworm and though females were more infected (5.9%) than males (2.0%), It was not statistically significant. The work of Iwu et al., (2016) in Imo state, reported a prevalence of (11.4%) for hookworm and that the age range of 10-12 years had the highest prevalence of (50%) and also that males (58.3%) had more prevalence than female (31.3%) respectively. The study of Walana et al., (2014) reported a prevalence of (0.3%) age range of 10 -19 years had the highest prevalence of (10.8%) while females to males ratio of prevalence showed a value of 62.7% to 37.3%
Transmission of hookworm
Hookworm infective larvae enter the body usually in the feet by penetrating the skin. A. Duodenale may also be acquired by oral route by direct ingestion of infective larvae through contaminated fruits & vegetables. Transmission is perennial in many tropics in cooler and drier climates. Transmission may take place in the warmer and wet season.
Diagnosis of hookworm
Diagnosis of hookworm depend on finding characteristic worm eggs on microscopic examination of stool samples using both wet preparation and concentration methods, although this is not possible in early infections. Early signs in small children may be anal itching, abdominal distension and pains and later anaemia. Adult worms are rarely found in stool samples. Other forms of detecting hookworm includes
- Eosinophila
Peripheral eosinophila can be found particularly during the phase of larvae migration and other stages of the infection. eosinophil level may be as high as 5-12%
2. Serological method
Infected individual make antibodies to hookworm which can be detected. This can be done through either the use of polymeric chain reaction (PCR) or high resolution melting curve (HRM). These target, the second nuclear internal transcribed space of the nuclear ribosomal DNA as the antigenic marker.
Prevention of hookworm disease
The infective larvae develop and survive in the environment of damp dirt particularly sandy and loamy soil times there for the main life of precaution are those detected by good hygiene behaviours
- Do not defecate in the open latrine toilets
- Do not use untreated human excreta or raw sewage as fertilizer in agriculture area
- De worm pets (dogs) and children regularly as the case may be
- Dispose off diapers properly
- Wash hands with soap and water before handling food
- Avoid contaminated food and water if you travel to areas where hygiene and sanitation are poor
- Wash peels or cook all raw vegetable and fruit before eating
References
Abah E, and Prne I (2015): Status of intestinal parasitic infected among primary school children in Rivers state. Nigeria J. of Parasitology Research 93:90:
Adenusi A and Ogunyoni O (2008): Prevalence of human hookworm species in urban community. Afr J Bioteeh 2:470-473.
Aneja J (2008): Soil transmitted infection hookworm, ascaris and trichuria infections. West Afri Para 367: 120- 130
Bethony F, Brooker Hotez P (2008): Soul transmitted health infection. Lancet 367: (9621) 1521-1533
Bundy Walker T, Lozoff B (2009): Child development risk factor for adverse infection in Africa. Lancet 639:145-157
Center for Disease Control and Prevention (CDC) (2008): Hookworm. CDC factsheet
Chan IM, Medly, D, Buney D, (2017): The evaluation of potential global morbidity attribute to intestinal nematode infections. Parasitol 109:373-387
Debenoist B, Egli F, Cogswell, M (editors) (2008): Worldwide prevalence of anaemia. Geneva: World Health Organization sheets pp16-25
Fenwide A (2012): The global burden health 126 (3) 233-236
Gasser R, Cantacessi E, Campbell B (2009). Improved diagnostic tools for human hookworm. Rev mod Deagn 9 (1): 1721
James, W and Berger, T (2008): Andrew disease of the skin: Clinical Deymatology. Saunders Elsevier publishers pp.435
Hotex P (2009): Mass drug administrative and integrated control for the words high prevalence neglected tropical disease. Clin Pharmacol Ther 85: 659-664
Hotex P , Bethony J, Diemert P, (2010): Developing vaccines to cerbat hookworm infection and intestine selustosomiasis Nat. Rev Neurobiol 8:814-826
Liviur R, Ikeanyba M, Azoro A (2016): Hookworm and Searic infection among school aged children in Eluime Imo State. J. Bacteria Paraterol 7.278
Markell E, John D (ed) (2008): Marked and Voges Medical Parasitology (9th ed). St. Louis: Elsevier Saunder pp 6-9
Mildzi, N Mtayom-zinyowere S, Sangiwere (2010): Consequences of polyparentisn on anaemia among primary school children. Deta Trp 115 (1-2): 103-111
Nwosu, K (2011): Human infection in Nigeria. Nig J Parasitol 50 (2) 44- 452
Odebunia J. Ezeamani A. Costa L (2007): Functional significance of low intensity population of helmith infection. Am J. Infect Dis 94: 2610- 2670
Olusola o, Adegbayi M, Akeem A (2011): Asymptomatic falapamain malaria intestinal helminet co-infection among school children in Osogbo, Nigeria. J. Res Med Sci 16(5): 680 – 686.
Williams W, Adoo E, Tay S, (2013): Prevalence of hookworm 4 (suppl) 158-161
World Health Organization (WHO) (2007). School deworning at glance WHO Fact Sheet (supp16) 20-4
Udosi J (2007): Studies on the co-occurrence of the two speices of hookworm in riverine community in Nigeria. Parasitol 35:341- 349.
