LITERATURE REVIEW
2.2 EFFECTS OF DRUG TREATMENT ON THE PREVALENCE OF URINARY SCHISTOSOMIASIS:
Chemotherapy plays a major role in the control of schistosomiasis. It decreases its prevalence, morbidity and transmission.35 The method of delivery of the drug could be mass, targeted, selected (population or group) and phased chemotherapy depending on the prevalence of the disease, population concerned, objectives of the control programme and the resources available. There are many drugs with different properties one can choose from but the properties of an ideal drug are: 15
1. Safety: the consumption of the drug should not cause injury to the subject/
patient.
2. Dosage forms: A single dosage drug formulation is an additional advantage especially for community or large-scale usage.
3. Route of administration: A drug with oral formulation is preferred for ease of administration because it does not require special technique for administration.
4. Efficacy: the drug should be effective against the disease.
5. Side effects: the drug should have only minimal and transient side effects.
6. Stability: it should be stable during storage and when consumed.
No major changes have occurred during the past twenty (20) years regarding the therapeutic tools available to the clinician for the treatment of schistosomiasis. If any it is that the two drugs (oxamniquine and metrifonate) that are valuable alternatives to the drug of choice (praziquantel) have become more difficult to procure in some African countries.39 Praziquantel (Isoquinoline-4-one) is effective in the treatment of all forms of schistosomiasis with only minimal transient side effects, while oxamniquine (a nitroquinolone) is used exclusively to treat intestinal schistosomiasis in Africa and South America. The only alternative to praziquantel in the treatment of urinary schistosomiasis, metrifonate, is effective only for the treatment of urinary schistosomiasis. 39 Extensive toxicological studies have been carried out by WHO in collaboration with the International Agency for Research on Cancer to establish the safety margin of these drugs.5 The studies conclusively showed no mutagenic, carcinogenic, embryo toxic or teratogenic activity from them. Also a systematic analysis of existing literatures to compare the therapeutic and operational profiles of metrifonate and praziquantel was done. Therapeutic efficacy of either of the drugs (praziquantel and metrifonate) against Schistosoma haematobium, impact on pathology commonly associated with Schistosoma haematobium infection, frequency, type and duration of adverse reactions were some of the criteria used in the comparison of the drugs. Health risks associated with inadvertent over dosage, applicability and practicability of treatment in various medical settings, tolerance and resistance, pharmacological properties, toxicity and economic aspects were other criteria used. It was concluded that both medical and operational criteria indicate
that praziquantel is superior to metrifonate for the treatment of urinary schistosomiasis40. Another disadvantage of metrifonate is the fact that it has to be given in multiple doses.
This makes its difficult for control programmes especially where the community has poor perception and participation in control programmes.
It is pertinent to note that though praziquantel is effective, minimal egg output coupled with the fact that praziquantel is ineffective in the treatment of early infection, could sustain the transmissionof the disease if mass chemotherapy is carried out. This is because praziquantel treatment may result in loss of immunity in those with light infections, thus placing them at risk of having high egg output later, unless other control measures were put in place.5 Consequently, the organizational and operational requirements of chemotherapy (praziquantel) in addition to high re-infection rate, the need for follow ups and re–treatment places an unbearable burden on the health budget of most developing countries. Additionally, re-infection rate and recommencement of egg excretion among those that had received treatment has been found to be very high as was reported in Niger41, Egypt23 and Malumfashi.5 Consequently, it is concluded that chemotherapy must be combined with other control measures such as health education, molluscicide application or provision of potable water and improvement in sanitation to achieve any lasting benefits.10
A study to evaluate the efficacy of mass chemotherapy, using praziquantel on Schistosoma haematobium infection in a rural village in Egypt, showed that one year after treatment, there was a 60-fold reduction in the estimated population egg count from 10,006 to 167 with the greatest benefit in the childhood age groups, thus demonstrating the feasibility of mass chemotherapy effective method to reduce Schistosoma
haematobium infection. 39 However, for practical purposes, a drug with less than 50%
chance of killing the worms is not recommended. The different brands of praziquantel for example, sold at different prizes produce different levels of efficacy. It also produces a complex non-linear relationship between drug efficacy and cost-effectiveness, with drugs of low efficacy producing high and variable cost-effectiveness ratios.42 The other problem with praziquantel is that host-related factors could cause low cure rates of praziquantel for the treatment of schistosomiasis. The factors incriminated in low cure rates are immunodeficiency (such as HIV infection) and very high egg counts.43 A study conducted in Senegal using four discrete cohorts revealed that the lowest cure rate was among the group with the highest egg count.43 Also, when the effect of HIV infection was tested among two groups of population heavily infected with schistosoma egg counts, it was revealed that both groups of those that are HIV positive those that are HIV negative responded in a similar magnitude to praziquantel treatment.44 In line with effect of host-related factors on cure rates is the possibility of the emergence of resistance by some strains of schistosoma species to praziquantel. Studies conducted in two endemic countries (Egypt and Senegal) have also demonstrated development of resistance by schistosoma species under sustained drug pressure.45
2.3 KNOWLEDGE AND PRACTICES OF THE COMMUNITY ABOUT URINARY SCHISTOSOMIASIS:
Health behaviours adopted in childhood and adolescence as a result of primary socialization within the family are passed on from one generation to another without questioning. Thus in the absence of factual information, proper and appropriate guidance,
children are likely to adopt attitudes and behaviours that are detrimental to their health and the health of others in the family and community in general. However, attitudes are known to be specific and often less enduring. They are therefore likely to change over time. Behavioural risks are also modifiable and sometimes they do change rapidly as a result of timely and appropriate health education. Urinary schistosomiasis affects only humans and its transmission is greatly affected by ignorance of its cause and mode of transmission, misconceptions, false cultural beliefs, unavailability of functional social amenities such as health facilities and services and poor hygienic practices.5,10
A study conducted in Yola, Adamawa state of Nigeria, looked at the effect of modification of behaviour and attitude in the control of schistosomiasis, and found that specific knowledge about the parasite, its vector and the interaction between the parasite and vector were extremely low.46 One stream, which was identified as the main transmission point with bathing / swimming and fishing as the main activities predisposing people to schistosomal infection, was continuously used by the community.
This was attributed to the lack of knowledge of the relationship between the stream and schistosomiasis. Low level and or lack of knowledge about urinary schistosomiasis were demonstrated in different parts of Nigeria: 65.7% of primary school pupils in Ile-Ife, South-western Nigeria, did not know what causes urinary schistosomiasis47; 91.7% of residents in Bakalori, Northeast Nigeria, did not know the cause of urinary schistosomiasis among others.5
Different studies in South–Eastern Nigeria48 and Cameroon49 revealed that females tend to have more stable infections than males. Both studies attributed the higher infection in females to their gender assigned domestic and agricultural responsibilities,
which increases their exposure to the sources of the infection. These include fetching water, bathing children, laundering, cleaning of utensils, preparation and washing of foodstuffs, and farming. Consequent to lack of knowledge about the transmission of the disease, marriage opportunities for affected females may be diminished, as parents of unmarried daughters with urinary schistosomiasis are obliged to inform potential suitors of the infection.48, 49 In many cases, men refuse to marry an infected girl, in the belief that she has an infectious venereal disease. This thinking also affects married women who were infected.49 In some communities in South–Eastern Nigerian, they are forbidden any form of sexual contact with their husbands until they are cured, and may even be ejected from the household.48 This goes contrary to the belief held by many African societies that
urinary schistosomiasis in men (“red water”) is a sign of coming of age and virility.48 Still in parts of Ghana some communities attributed the red colour of the urine to the red
colour of a variety of sugar cane eaten in the area50. Thus, the social stigma attached to urinary schistosomiasis in some communities in conjunction with financial limitations, discourages infected women from seeking medical help. This may contribute to the prevalent view that males are generally more exposed to the infection through occupational and recreational exposure and greater morbidity than females. For example, in parts of Tanzania, urinary schistosomiasis is considered a shameful disease and infected individuals prefer consulting ‘Traditional healer’ than to health personnel51. It is therefore likely that urogenital schistosomiasis infections in women are significantly under reported in many societies. Other factors that affect health-seeking behaviour in urinary schistosomiasis patients include: perception of disease as ‘not serious enough’52;
‘lack of money’ (poverty) 52;
2.4 IMPACT OF HEALTH EDUCATION ON PREVALENCE OF URINARY