Malaria and Filariasis Lecture Notes

Overview of Malaria and Public Health Impact

• Definition: Malaria is a protozoal infection of the genus Plasmodium. It is caused by the female Anopheles mosquito and is clinically characterized by fever, joint pains, and vomiting.

• Transmission: The Plasmodium protozoa are transmitted to humans through the bite of a female Anopheles mosquito.

• Global and Local Significance:

  • Malaria is a leading communicable disease affecting a large segment of the population in many developing countries.

  • In Zambia, it is a major public health concern, particularly involving pregnant women and children under the age of $5$ years.

• Zambian Statistics and Morbidity:

  • It is a leading cause of morbidity and mortality in Zambia.

  • Accounting for approximately $3,000,000$ clinical cases annually.

  • Results in roughly $50,000$ deaths per year.

  • In-patient cases: Malaria accounts for an average of $62.1\%$ of all hospital admissions in Zambia today.

Malaria Species and Prevalence

• Species Identification: There are four primary species of malaria parasites:

  • P. falciparum: Responsible for $95\%$ of all malaria cases in Zambia.

  • P. malariae: Comprises approximately $3\%$ of cases.

  • P. ovale: Comprises approximately $2\%$ of cases.

  • P. vivax: Considered very rare within the Zambian context.

Facts About Malaria Transmission

• Vector Mechanics:

  • Transmission occurs from one person to another via the bite of a female Anopheles mosquito.

  • Biting Patterns: The female mosquito typically bites during dusk and dawn.

  • Nutritional Requirements: The female requires a blood meal (human protein) to nourish her eggs.

  • Role of Male Mosquitoes: Male mosquitoes do not transmit malaria; they feed on plant juices rather than blood.

• Vector Diversity:

  • There are approximately $380$ species of Anopheles mosquito, but only about $60$ are capable of transmitting malaria.

• Breeding Environment: Anopheles mosquitoes breed in water. Consequently, the accumulation of water and swampy conditions favors the spread of the disease.

Risk Factors and Vulnerable Populations

• Age-Based Risk: Children below the age of $5$ years.

• Biological Risk: Pregnant women.

• Environmental/Behavioral Risk:

  • Individulals not sleeping under Insecticide-Treated Nets (ITNs).

  • Proximity to swampy or water-logged areas.

• Immunological Risk: Tourists and individuals returning from non-malarious areas are highly prone to infection due to a lack of naturally acquired immunity.

Pathogenesis and Life Cycle of Plasmodium

• Infection Flow: The parasite infects the human and insect hosts alternatively. The life cycle consists of three primary phases:

I. Hepatic, Tissue, or Pre-erythrocytic Phase

• Inoculation: During feeding, mosquito saliva containing primitive stages of the parasite, called sporozoites, is injected into the human bloodstream.

• Liver Invasion: Sporozoites migrate to the liver, where they invade and develop within hepatocytes.

• Rupture: The infected hepatocyte eventually ruptures, releasing merozoites into the system.

II. Erythrocytic Phase

• RBC Invasion: Merozoites invade red blood cells (RBCs).

• Lysis and Symptoms: The red cells eventually lyse (burst), releasing parasites and metabolic byproducts. This process triggers bouts of fever and the characteristic clinical symptoms.

• Replication: The cycle repeats as more merozoites move on to invade healthy red cells.

III. Sexual Phase

• Gametocyte Development: Sexual forms of the parasite (gametocytes) develop in the human host.

• Ingestion: These are ingested by another female Anopheles mosquito during a blood meal.

• Gut Development: The parasites develop into sporozoites within the gut of the insect host.

• Migration: Sporozoites travel to the mosquito's salivary glands, making the vector ready to infect another human host.

Clinical Picture and Malarial Paroxysm

• Incubation Period: Typically ranges from $9$ to $14$ days.

• Malarial Paroxysm: Sudden attacks comprising three distinct clinical stages:

1. The Cold Stage

• Symptoms: Extreme cold sensation; the patient may seek direct sunlight.

• Physiological Cause: Triggered by the rupture of RBCs and the release of parasites into the bloodstream.

• Features: Shivering; nausea and vomiting; intense headache.

• Temperature: Fever can reach between $38^{\circ}C$ and $40^{\circ}C$.

• Complications: Hemolytic anemia may occur due to severe hemolysis.

2. The Hot Stage

• Duration: Lasts approximately $2$ to $6$ hours.

• Symptoms: The patient feels extremely hot and may become delirious. It is characterized by a full, bounding pulse and dry, burning skin.

• Temperature: May exceed $41^{\circ}C$.

• Associated Features: Persistent intense headache, nausea, and vomiting.

3. The Sweating Stage

• Duration: Lasts approximately $2$ to $4$ hours.

• Symptoms: Profuse sweating as the body temperature drops rapidly to below normal levels.

• Outcome: The patient feels slightly more comfortable and typically falls into a deep sleep, waking up feeling weak.

General Clinical Features and Diagnosis

General Features

• Severe Headache: Caused by increased oxygen demand in the brain.

• Fever: Resulting from the presence of parasites in the blood.

• Malaise: Caused by reduced oxygen tension.

• Muscle/Joint Aches: Generalized body weakness.

• Neurological Signs: Drowsiness, delirium, and confusion due to reduced oxygen supply to the brain.

• Gastrointestinal Issues: Poor appetite (impaired blood supply to the GIT) and yellowish vomiting.

• Jaundice: Mild jaundice caused by the destruction of RBCs.

Diagnosis

• Blood Slide: Microscopic examination for malaria parasites (positive result).

• Rapid Diagnostic Test (RDT): Blood sample test for specific antigens (positive result).

• Clinical Presentation: Observation of features such as muscle aches and yellowish vomitus.

• Hemoglobin (Hb): Blood test to assess for and rule out anemia.

Classification of Malaria

• I. Uncomplicated Malaria: Infection without life-threatening manifestations.

• II. Severe Malaria: Characterized by life-threatening manifestations, including:

  • Prostration: Generalized weakness; inability to sit, stand, or walk without support.

  • Impaired Consciousness: Confusion, drowsiness, or coma.

  • Respiratory Distress: Fast breathing, particularly noted in children.

  • Circulatory Collapse and Shock.

  • Renal Failure.

  • Hyperparasitemia: High levels of parasites in the blood.

  • Severe Anemia.

Treatment Protocols for Malaria

I. Uncomplicated Malaria

• Goal: Prompt treatment to prevent progression to severe malaria.

• First-Line (General): Artemether-Lumefantrine (Coartem).

• Pediatric Exception: Children weighing less than $10\,kg$ should be started on the second-line drug, Artesunate.

• Pregnancy Protocol: Pregnant women in their first trimester should be treated with Quinine as the first-line treatment for uncomplicated malaria.

Coartem Dosage Schedule (Stat, then 8h, then Every 12h)

II. Severe Malaria (Second-Line Treatment)

• Artesunate: Preferred for adults, children, infants, pregnant women (all trimesters), and lactating women. Administered intravenously (IV) or intramuscularly (IM) for at least $24\,h$. Once stable and able to tolerate oral medication, complete with $3$ days of ACT (Artemisinin-based Combination Therapy).

• Artemether: Parenteral alternative if Artesunate is unavailable; preferred over Quinine for children and adults.

• Quinine (Alternative):

  • Loading Dose: $20\,mg/kg$ body weight in $500\,mL$ of $10\%$ or $5\%$ Dextrose over $4\,hours$. Followed by a $4\,hour$ resting phase.

  • Maintenance Dose: $10\,mg/kg$ salt administered at $8\,h$ intervals (starting $8\,h$ after the first dose). Typically $2-3$ parenteral doses before switching to oral.

  • Oral Transition: Quinine $600\,mg$ TDS (three times a day) for $5 \text{ to } 7$ days.

III. Supportive Care

• Dextrose: $50\%$ bolus given IV slowly if Random Blood Sugar (RBS) results indicate hypoglycemia.

• Convulsion Control: Diazepam $1 \text{ to } 2\,mL$ (monitor for drug-induced unconsciousness).

• Blood Transfusion: Required to correct severe anemia.

• Antibiotics: Used to treat secondary bacterial infections.

Nursing Problems and Diagnostics

• Potential for Fluid Volume Deficit: Related to high-grade fever and vomiting.

• Altered Nutrition (Less than body requirement): Related to reduced blood flow to the GIT; evidenced by weight loss.

• Knowledge Deficit: Related to the manifestations of infection; manifested by a lack of questioning.

• Risk of Injury: Related to potential convulsions.

• Disturbed Sleep Pattern: Related to restlessness and joint pain.

WHO Complications of Severe Malaria

• Impaired Consciousness: Glasgow Coma Scale (GCS) < 11 in adults or Blantyre Coma Score < 3 in children.

• Prostration: Inability to sit or stand without assistance due to hemolysis or low glucose.

• Multiple Convulsions: More than two episodes within a $24\,h$ period.

• Acidosis: Base deficit > 8\,mEq/L; plasma bicarbonate < 15\,mmol/L; or venous lactate > 5\,mmol/L.

• Hypoglycemia: Blood glucose < 2.2\,mmol/L (< 40\,mg/dL).

• Severe Malarial Anemia: Hemoglobin < 5\,g/dL (children) or < 7\,g/dL (adults); Hematocrit < 15\% (children) or < 20\% (adults).

• Renal Impairment: Serum creatinine > 265\,\mu mol/L ($3\,mg/dL$) or blood urea > 20\,mmol/L.

• Jaundice: Serum bilirubin > 50\,\mu mol/L ($3\,mg/dL$) with parasite count > 100,000/\mu L.

• Pulmonary Oedema: Oxygen saturation < 92\%; respiratory rate > 30/min; radiologically confirmed.

• Significant Bleeding: Recurrent bleeding from gums, nose, or venepuncture sites; melaena.

• Shock: Capillary refill time $\ge 3\,s$ or temperature gradient on legs.

• Hyperparasitaemia: P. falciparum parasitemia > 10\%.

Prevention Strategies for Malaria

• 1. Insecticide-Treated Nets (ITNs): Provide year-round protection; can reduce child mortality by up to $63\%$.

• 2. Chemical Control: Indoor Residual Spraying (IRS) and larviciding at least annually, specifically during hot/rainy seasons.

• 3. Environmental Modification: Clearing breeding sites, drainage maintenance, removing stagnant water and excess vegetation, and prohibiting unauthorized quarrying/irrigation.

• 4. Building Proofing: Installing mosquito screens on doors and windows of homes and public facilities.

• 5. Personal Protection: Use of mosquito coils, repellent aerosols, and wearing long-sleeved clothing (especially for infants).

• 6. Intermittent Presumptive Treatment (IPT):

  • Target: All pregnant women.

  • Regimen: $3$ treatment doses of Fansidar starting in the second trimester, administered at least once a month.

Introduction to Filariasis

• Definition: A parasitic tropical disease caused by filarial worms (nematodes) and transmitted through mosquito bites.

• Human Hosts: There are $9$ known filarial nematodes that use humans as a definitive host.

• Types of Filarial Worms:

  • Lymphatic Filariasis: Wuchereria bancrofti, Brugia malayi, Brugia timori.

  • Subcutaneous Filariasis: Onchocerca volvulus, Loa loa, Mansonella streptocerca, Dracunculus medinensis.

  • Serous Cavity Filariasis: Mansonella perstans, Mansonella ozzardi.

• Prevalence: Bancroftian variety (W. bancrofti) is found throughout Africa, including Zambia. Malayan filariasis (B. malayi) is limited to Southern and Southeastern Asia.

Life Cycle and Pathophysiology of Filariasis

Life Cycle

• Stages: Complex cycle consisting of $5$ stages.

• Reproduction: After mating, the female worm produces thousands of live microfilariae.

• Vector Intake: Microfilariae are taken up by a mosquito during a blood meal.

• Maturation: Within the insect, microfilariae molt into $3rd$ stage (infective) larvae.

• Inoculation: Larvae are injected into the human dermis during the next blood meal.

• Maturation to Adult: Takes approximately one year to reach the adult worm stage.

Pathophysiology

• Niche: In lymphatic filariasis, adult worms reside in lymphatic vessels near lymph nodes.

• Vascular Impact: Worms cause distortion and local inflammation. In advanced stages, they obstruct vessels, leading to tissue enlargement.

• Bancroftian vs. Malayan: W. bancrofti typically involves the legs and genitals; B. malayi typically involves the legs below the knees.

• Elephantiasis: Repeated inflammation leads to blockages and gross enlargement of limbs/genitals with coarse, thickened skin.

• Ocular Impact: In conjunctiva filariasis, larvae migrate to the eye. Untreated, this can cause Onchocerciasis (River Blindness).

Signs, Symptoms, and Diagnosis of Filariasis

Clinical Features

• Initial Signs: Chills, sweating, headache, and fever (appearing $3 \text{ to } 12\,months$ post-bite).

• Localized Signs: Redness, swelling, and pain in arms, legs, or scrotum.

• Lymphangitis: Inflammation of lymph vessels.

• Abscesses: May form due to dying worms or secondary bacterial infection.

• Occlusion Symptoms: Massive enlargement of the scrotum, legs, breasts, or labia minora.

Diagnosis

• Giemsa Stained Thick Film: Used to identify microfilariae.

• Nocturnal Periodicity: Blood must be drawn at night, as microfilariae circulate when the mosquito vector is most active.

• Other Methods: Polymerase Chain Reaction (PCR), lymph node biopsy (for adult worms), and X-rays (for calcified adult worms).

Treatment and Management of Filariasis

• Drug of Choice: Diethylcarbamazine (DEC).

  • Regimen: $6\,mg/kg/day$ for $1$ day (effective as a $12\text{-day}$ course).

  • Action: Kills microfilariae and some adult worms.

  • Side Effects: Dizziness, nausea, fever, headache, and muscle/joint pain (proportional to microfilarial load).

• Combo Therapy: Albendazole $400\,mg$ combined with Ivermectin $150 \text{ to } 200\,\mu g$.

• Antibiotics: Ampicillin $500\,mg$ QID for secondary infections.

• Supportive Care:

  • Antihistamines: Phenergan $5 \text{ to } 10\,mg$ at night to counteract effects of rapid microfilaria destruction.

  • Physiotherapy: Bandaging to manage lymphedema.

Prevention and Complications of Filariasis

Prevention

• Avoidance: Limit outdoor activity at night.

• Clothing: Wear long sleeves and pants; avoid dark colors.

• Repellents: Use insect repellents (DEET, citronella, lemon eucalyptus).

• Vector Control: Use of ITNs in communities where Anopheles is the primary vector. Mass Drug Administration (MDA) programs.

Complications

• Permanent Damage: Lymph system and kidney damage.

• Physical: Disfigurement (Elephantiasis) and severe pain from lymphatic congestion.

• Functional: Sexual disability.

• Social: Rejection and isolation due to severe physical disfigurement.