Study Notes on Communicable Diseases - Dengue Fever, Filariasis, Malaria, and Encephalitis

Communicable Diseases: Dengue Fever

• Overview of Dengue Fever

  • Acute febrile disease caused by Dengue virus

  • Transmitted primarily by mosquitoes, particularly the female Aedes aegypti

  • Known colloquially as "breakbone fever" due to severe muscle and joint pain

  • Can lead to serious conditions like Dengue Hemorrhagic Fever (DHF)

• Transmission

  • Transmitted by the bite of infected mosquitoes, specifically Aedes aegypti.

  • Other species: Aedes albopictus as a secondary vector

  • Breeds mostly in man-made containers with stagnant water

  • Active during the day, especially two hours after sunrise and before sunset

• Causative Agents

  • Dengue virus (types 1-4) belonging to the Flaviviridae family

  • Other related viruses (arboviruses) and Aedes mosquitoes as vectors

• Symptoms of Dengue Fever

  • High fever, rash, pain behind eyes, joint and muscle pain

  • Petechial rash indicating bleeding under the skin

  • Thrombocytopenia (low platelet count) and leukopenia (low white blood cell count)

  • Classic signs: fever, rash, muscle pain (Dengue triad)

• Diagnostic Tests

  • Thrombocytopenia confirmed by platelet count < 100,000/mm³.

  • Rumpel-Leed test (tourniquet test) to assess capillary fragility:

  • Apply pressure on arm and wait for petechiae appearance

  • Positive if >20 petechiae per square inch

  • Hemoconcentration indicated by hematocrit increase of at least 20%

  • Occult blood testing for coagulopathy signs

• Clinical Manifestations

  • Dengue Fever (DF): Fever, malaise, anorexia, chills, arthralgia, backache, and rash

  • Dengue Hemorrhagic Fever (DHF): Fever, hemorrhage, hepatomegaly, hypovolemic shock, and positive tourniquet test

  • Progression from DHF to Dengue Shock Syndrome (DSS) if untreated

• Phases of Illness

  • Initial Febrile Phase: 39°C to 40°C fever, headaches, rash, positive tourniquet test

  • Circulatory Phase: Occurs on days 3-5, decreased temperature, profound circulatory changes, cold clammy skin

  • Symptoms may progress to shock or death within a few days if untreated

• Classification of Severity

  • Grade 1: Fever + positive tourniquet test

  • Grade 2: Grade 1 symptoms + spontaneous bleeding

  • Grade 3: Grade 2 symptoms + circulatory failure (weak pulse, hypotension)

  • Grade 4: All Grade 3 symptoms + profound shock and organ failure

• Medical Management

  • No specific antiviral therapy; treatment is supportive

  • Symptomatic treatment for headache, ocular pain, and muscle pain

  • Intravenous fluids for dehydration, blood transfusions for severe bleeding

  • Ongoing monitoring of fluid balance critical to prevent complications

• Nursing Management

  • Maintain mosquito-free environment, observe vital signs

  • Medications for headache relief, elevation and ice packs for epistaxis

  • Position in Trendelenburg for shock

• Prevention Strategies

  • Community-based interventions (4 PM habit): Search and destroy mosquito breeding sites

  • Use of mosquito nets, larvivorous fish, and environmentally sound practices

  • Awareness programs by health authorities to educate communities on preventing dengue

Filariasis

• Overview

  • Lymphatic filariasis is a parasitic disease caused by microscopic thread-like worms

  • Leads to severe disability and disfigurement (elephantiasis), but rarely fatal

• Transmission

  • Transmitted by blood-feeding insect vectors, primarily mosquitoes

  • Three primary species involved: Wuchereria bancrofti, Brugia malayi, and Brugia timori

• Clinical Manifestations

  • Initial chills, fever, and swelling of lymph nodes after infection, leading to chronic lymphedema and elephantiasis

  • Swelling of limbs, scrotum, and breast regions

• Diagnostic Evaluations

  • Circulating Filarial Antigen (CFA) test performed via finger prick

  • Blood samples collected at night when larval concentration is highest

  • Ultrasound for lymphatic obstruction assessment and tissue biopsy for cutaneous filariasis

• Treatment

  • Medications include ivermectin, albendazole, and diethylcarbamazine (DEC)

  • Surgical intervention may be necessary for excessive tissue removal and drainage

  • Health education key for prevention, emphasize environmental sanitation and elimination of breeding sites

Malaria

• Overview

  • Acute and chronic parasitic disease transmitted by the bite of infected female Anopheles mosquitoes

  • Known as "mars fever" historically, characterized by cyclical fever patterns

• Clinical Manifestations

  • Cyclical paroxysms of chills, fever (40-42°C), and profuse sweating

  • Symptoms include headache, malaise, anemia, and myalgia

• Causative Agents

  • Caused by four Plasmodium species:

  • Plasmodium falciparum (most deadly), Plasmodium vivax, Plasmodium malariae, Plasmodium ovale

  • Transmission occurs via Anopheles mosquito bites, blood transfusion, or using shared needles

• Diagnosis

  • Malaria smear is the gold standard for detecting parasites during fever spike

  • Rapid diagnostic tests available for quick results in the field

  • Other tests include examining spleen tissue through biopsy

• Medical Management

  • Treatment with anti-malarial drugs such as Artemether-lumefantrine and can include supportive care for severe cases

  • Assess complications such as renal failure or neurologic toxicity from medications

• Prevention Strategies

  • Eradication of breeding sites, environmental sanitation, and use of insecticides

  • Blood screening and discouragement of blood donation in endemic areas

Encephalitis

• Overview

  • Acute inflammatory infection of the brain, often resulting from viral or bacterial diseases

  • Presentations include severe neurological dysfunction, also known as brain fever

• Causative Agents

  • Common viral causes: Herpes simplex, West Nile virus, Japanese encephalitis virus

  • Bacterial infections and parasitic infections also contribute

• Clinical Manifestations

  • Early signs: fever, headache, dizziness, and vomiting

  • Late signs: nuchal rigidity, seizures, confusion, ataxia, tremors, and potential coma

• Diagnosis

  • Confirmatory serologic tests for viral antibodies

  • Cerebrospinal fluid analysis through lumbar puncture

  • MRI and EEG may also be utilized for further evaluation

• Medical Management

  • Supportive treatment focused on symptoms management

  • Corticosteroids may reduce inflammation

  • Physical and occupational therapy may be beneficial for recovery

• Prevention Strategies

  • Effective prevention primarily through vector control measures, including mosquito management and environmental clean-up

  • Education on preventing bites and recognizing early signs of illness to seek timely medical attention.