Chapter 3: Identify microbial and parasitic diseases

Microbial and parasitic diseases constitute a major public health concern in Kenya, especially for community health professionals tasked with prevention, control, and management at the grassroots level. Understanding the various types of these diseases, their causative agents, modes of transmission, clinical features, and public health implications is essential for effective intervention. This chapter focuses on three prevalent disease groups in Kenya: tuberculosis (TB), sexually transmitted infections (STIs), and malaria. Each disease is explored with a view to equipping community health workers with knowledge that supports early detection, patient education, and community-based prevention strategies.

3.1 Common types of microbial and parasitic diseases

Microbial and parasitic diseases are a major public health concern in Kenya and a daily concern for community health professionals who work in prevention, early recognition and referral at the grassroots. A microbial disease is caused by a microbe such as a bacterium, a virus or a fungus. A parasitic disease is caused by a parasite such as a protozoan, a worm or an ectoparasite. This topic introduces four common examples: amoebiasis, tuberculosis (TB), sexually transmitted infections (STIs) and malaria. Cholera, typhoid, measles, polio and flu follow in their own topics.

Amoeba

Amoebae are single-celled protozoa that move by stretching out parts of their body called pseudopodia. Most amoebae live freely in soil and water and do not harm people. Entamoeba histolytica is the amoeba that causes amoebiasis, an infection of the large intestine that is also called amoebic dysentery when it causes bloody diarrhoea. It occurs wherever sanitation and drinking water are unsafe.

• How it spreads: The infective stage is the cyst, which is passed in the faeces of an infected person and survives for a long time in moist conditions. People swallow cysts in water, vegetables or other food contaminated with faeces, or on unwashed hands. Flies can carry cysts from faeces to food.
• What happens in the body: In the intestine the cyst releases the active, feeding form, the trophozoite, which can invade the lining of the large intestine and cause ulcers.
• Signs and symptoms: Many infected people have no symptoms. Intestinal disease causes abdominal cramps and diarrhoea with blood and mucus, and a painful urge to pass stool. If the amoebae reach the liver they cause an abscess with fever and pain in the upper right side of the abdomen.
• Diagnosis: A laboratory worker examines fresh stool under the microscope for trophozoites and cysts. Entamoeba histolytica looks the same under the microscope as harmless amoebae of the gut, so the result is read together with the signs and symptoms. Bloody diarrhoea can also be caused by bacteria, so it cannot be told apart from amoebiasis without a laboratory test.
• Treatment: A health worker prescribes metronidazole or a similar medicine to treat invasive disease, followed by a second medicine that clears the cysts left in the gut. Dehydration is treated with oral rehydration solution.
• Prevention: Use safe water, wash hands with soap after using the toilet and before handling food, wash raw vegetables and fruit in safe water, use latrines, keep food covered from flies and treat infected people.
• Other amoebae: Naegleria fowleri is a rare amoeba that lives in warm fresh water and can cause a severe brain infection when water enters the nose, for example during swimming in warm ponds.

Role of the community health promoter: recognise a child or adult with bloody diarrhoea, give oral rehydration solution, refer promptly for testing and treatment and teach hygiene and safe water practices to the household.

3.1.1 TB

Tuberculosis, usually called TB, is a significant infectious disease in Kenya that occurs in both urban and rural communities. Community health professionals play a central role in TB control through case finding, support for treatment adherence and community sensitisation. TB is closely linked with HIV and has drug-resistant forms, which makes its control complex.

Epidemiology and transmission of TB

TB is caused by the bacterium Mycobacterium tuberculosis, which spreads through the air in droplets when a person with lung TB coughs or sneezes. People are more likely to be infected where they share crowded, poorly ventilated spaces, such as a crowded household or a packed public transport vehicle, and people with weak immunity are more likely to become ill, in particular people living with HIV, people who are undernourished and people with diabetes. Many infected people have latent TB, in which the bacteria are present but cause no symptoms and are not infectious. Latent infection can progress to active disease later, and only people with active lung TB spread the bacteria to others.

Clinical features and diagnosis

TB most commonly affects the lungs (pulmonary TB), but it can also involve lymph nodes, bones and the brain coverings (extrapulmonary TB). Symptoms include a cough lasting two weeks or more, chest pain, weight loss, night sweats and fever. A person with any of these symptoms is referred for testing. Diagnosis often begins with sputum testing, either by smear microscopy or by a rapid molecular test such as GeneXpert, which detects the TB bacterium and tests for resistance to rifampicin. Chest X-ray and clinical evaluation complement the laboratory tests, particularly for TB outside the lungs.

Treatment and drug resistance

Standard treatment for drug-susceptible TB lasts six months: two months with four medicines (isoniazid, rifampicin, pyrazinamide and ethambutol) followed by four months with isoniazid and rifampicin. TB treatment is provided free of charge in public health facilities. Community health promoters support directly observed treatment, in which a trained supporter watches the patient swallow the medicines, so that the course is completed and treatment failure is prevented. Drug-resistant TB, including multidrug-resistant TB (MDR-TB), which resists at least isoniazid and rifampicin, arises when treatment is incomplete or wrong, and it can also be passed directly from one person to another. It needs longer, more toxic and more costly treatment. Early detection of resistance by molecular testing guides the choice of regimen.

Public health strategies and community role

Community health promoters contribute to TB control in several ways:

• Active case finding: They screen household members and neighbours for cough, fever, night sweats and weight loss and refer anyone with these symptoms.
• Contact tracing: They identify household members of a person with TB, since contacts are at higher risk. Children under five years who live with a person with TB and people living with HIV may be offered preventive treatment by the health facility.
• Treatment support: They remind patients to take medicines every day, check on side effects and find those who miss appointments.
• Prevention of spread: They teach covering the mouth when coughing, opening windows to improve ventilation and attending the facility early. BCG vaccination at birth protects young children against severe forms of TB.
• Stigma reduction: They explain that TB is curable and that people on treatment can live normally, which encourages those affected to seek care.
• Linkage with HIV services: TB services are linked with HIV programmes in health facilities, which improves outcomes for people with both infections.

3.1.2 STIs

Sexually transmitted infections (STIs) are a significant public health challenge in Kenya. They affect reproductive health, can harm unborn and newborn babies and increase the risk of HIV infection. Community health workers educate communities, promote safe sexual practices and help people to reach diagnosis and treatment. STIs are caused by bacteria, viruses and a protozoan, so their presentation and treatment differ.

Common types and causative agents

• Gonorrhoea: Caused by Neisseria gonorrhoeae, a bacterium that causes discharge from the urethra or the vagina and pain on passing urine.
• Chlamydia: Caused by Chlamydia trachomatis, a bacterium that often causes no symptoms, especially in women, but can lead to pelvic infection and infertility.
• Syphilis: Caused by the spirochaete Treponema pallidum, which causes a painless genital ulcer first and later widespread illness, and which can pass from the mother to her unborn baby.
• Genital herpes: Caused by the herpes simplex virus, which causes painful recurrent blisters and ulcers.
• Human papillomavirus (HPV): A virus that causes genital warts and some types cause cervical cancer.
• Trichomoniasis: Caused by the protozoan Trichomonas vaginalis, which causes vaginal discharge and itching.
• HIV and hepatitis B: Viruses that can also be passed sexually and are considered with the STIs because they share prevention methods.

Clinical manifestations and diagnosis

STIs may present with genital ulcers, an abnormal discharge from the vagina or penis, itching, pain on passing urine, lower abdominal pain or swelling of the scrotum, or they may cause no symptoms at all, especially in women. In places where laboratory tests are limited, health workers use syndromic management, in which treatment is chosen according to the group of signs the patient has, such as urethral discharge or genital ulcer. Laboratory tests, including microscopy, culture and blood tests, give a definite diagnosis in facilities that offer them. Screening of groups with higher exposure, including adolescents and key populations, helps early detection.

Treatment protocols and prevention

Treatment depends on the cause. Bacterial infections respond to antibiotics: for example ceftriaxone is used for gonorrhoea, doxycycline for chlamydia and benzathine penicillin for syphilis. Viral infections such as herpes are managed with symptom relief and antiviral medicines when needed. Prevention rests on:

• Condom use: Correct and consistent use of male or female condoms reduces the risk of most STIs.
• Partner notification and treatment: Sexual partners of a patient are informed and treated, so that the infection is not passed back.
• Counselling and testing: Every person with an STI is offered counselling and an HIV test.
• Antenatal screening: Pregnant women are tested for syphilis and HIV, so that treatment can protect the baby.
• Vaccination: HPV vaccination protects girls against HPV infection and reduces the risk of cervical cancer later in life, and hepatitis B vaccine is given in infancy.

Community health interventions and challenges

Community health promoters give STI education, promote behaviour change communication and support partner tracing. Cultural beliefs, stigma and gender dynamics often make it difficult to discuss sexual health openly, which makes prevention harder. Combining STI services with reproductive health and HIV programmes improves access and reduces missed opportunities for care. Continuous training of community health personnel helps them to address emerging trends in STIs.

3.1.3 Malaria

Malaria is a disease of the blood and liver caused by Plasmodium parasites, which are protozoa, and it is spread by the bite of an infected female Anopheles mosquito. Unlike TB, which is caused by a bacterium, and measles, which is caused by a virus, malaria is a parasitic disease, and it is one of the main causes of illness in Kenya, especially in children under five years and pregnant women. This section presents malaria as a common disease in the community: where it occurs, who is at risk, how it is recognised and what the community health promoter does. The parasite species and life cycle, the clinical features and laboratory diagnosis and the control measures are developed in the later topic on Malaria.

Where malaria occurs in Kenya

Malaria does not occur at the same level everywhere. Kenya's malaria strategy groups the country into four zones according to how malaria is transmitted:

• Endemic areas: The lake region and the coast have transmission through much of the year, with peaks after the rains.
• Highland epidemic-prone areas: Transmission is usually low, but epidemics occur when warm temperatures and heavy rains allow mosquitoes and parasites to multiply.
• Seasonal transmission areas: Dry and semi-arid areas have transmission only in the short periods after rains.
• Low-risk areas: In the cool central highlands, transmission is very low.

Rainfall, temperature and altitude, and human activities that create breeding sites such as irrigation schemes, dams and poorly drained land, influence how much malaria there is at a given time.

Who is at risk

• Children under five years: They have not yet developed protective immunity and can become seriously ill quickly.
• Pregnant women: Malaria causes anaemia in the mother and can cause miscarriage, low birth weight and stillbirth.
• People living with HIV: Their weak immunity makes malaria more frequent and more severe.
• Visitors from low-risk areas: They have no immunity and can become seriously ill when they travel to endemic areas.
• Households without a net: People who sleep without an insecticide-treated net, or in houses near breeding sites, are bitten more often.

Recognising malaria in the community

Malaria is suspected in any person with fever or a recent history of fever, especially in an area with transmission. Other symptoms include chills, headache, body aches, vomiting and tiredness. These signs are shared with many other illnesses, so fever is confirmed with a malaria test before treatment is given. A person with any of the following danger signs has severe malaria and is referred to the facility at once:

• Convulsions: Fits during or after fever.
• Unable to drink or eat: Or repeated vomiting.
• Drowsiness or loss of consciousness: The person is unusually sleepy or cannot be woken.
• Difficulty breathing: Fast, laboured breathing.
• Severe paleness: Very pale palms, tongue and inner eyelids, which suggests severe anaemia.
• Dark urine or yellow eyes: A sign that red cells are breaking down in large numbers.

Treatment and why completing the course matters

The first-line treatment for uncomplicated malaria in Kenya is an artemisinin-based combination therapy (ACT), artemether-lumefantrine, taken as six doses over three days. Severe malaria is treated in a health facility with injectable artesunate. The community health promoter's task is to make sure the caregiver gives every dose, even after the fever has gone, because stopping early leaves parasites in the blood and encourages resistance. Medicines used in the past, such as chloroquine and sulfadoxine-pyrimethamine, are no longer used for treating malaria because of resistance. Sulfadoxine-pyrimethamine is still used in a different way, as preventive treatment for pregnant women.

Prevention in the community

The main protections are sleeping under an insecticide-treated net every night, indoor residual spraying where it is done, draining or filling breeding sites, preventive treatment for pregnant women at antenatal visits and, in the areas where the Ministry of Health has introduced it, the malaria vaccine for young children. The control measures are developed in the later topic on Malaria.

Role of the community health promoter in malaria

• Educate households: Explain how malaria spreads, why nets matter and why fever needs early care.
• Test and refer: Test fever with a rapid diagnostic test where trained and equipped to do so, and refer people with danger signs.
• Support treatment: Check that medicines are taken correctly and complete.
• Mobilise: Prepare the community for the rainy season through net checks, clearing of breeding sites and reminders to pregnant women to attend antenatal care.
• Report: Record malaria cases and referrals in the community health information tools, so that unusual increases are noticed early.

Chapter Summary

This chapter explored common types of microbial and parasitic diseases that significantly impact community health, beginning with tuberculosis, sexually transmitted infections, and malaria. It then examined cholera and typhoid, both of which are major concerns due to their transmission through contaminated food and water. The discussion included vaccine-preventable diseases such as measles and polio, highlighting their public health importance. Influenza was also covered as a widespread viral infection affecting diverse populations. The chapter revisited malaria to emphasize its complex transmission routes, including fecal-oral pathways, airborne spread, vector-borne transmission, fluid contact, and contaminated food and water. Understanding these modes of transmission is essential for effective prevention and control measures in public health settings.