A vector-borne disease is spread by a living carrier — usually an insect or a snail — that transmits the agent from one host to another. Control therefore targets three points at once: the agent (find and treat cases), the vector (remove breeding sites, protect people from bites or water contact), and the environment (sanitation, water management). The Department of Health (DOH) runs a separate program for each disease, delivered through local government health offices, rural health units, and barangay health stations.

Dengue in brief. Infection with one serotype gives lifelong immunity to that serotype only; a later infection with a different serotype carries a higher risk of severe disease. The illness has three phases: febrile, critical (around the time the fever falls, usually days 3–7, when plasma leakage can cause shock), and recovery (fluid reabsorbs, so watch for overload). WHO classifies cases as dengue without warning signs, dengue with warning signs, and severe dengue.

Warning signs of dengue — refer at once: abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation (ascites, pleural effusion), mucosal bleeding, lethargy or restlessness, liver enlargement, and a rising hematocrit with a rapid fall in platelets.

Malaria in brief. Classic paroxysms are cold stage (chills), hot stage (high fever), and sweating stage, recurring as red cells rupture. P. falciparum causes the most severe disease (cerebral malaria, severe anemia, kidney injury). P. vivax and P. ovale leave dormant liver forms that cause relapse.

Filariasis in brief. Adult worms live in lymphatics. Early infection is often silent; chronic disease causes lymphedema, elephantiasis, and hydrocele, with painful acute attacks (adenolymphangitis). Microfilariae circulate mainly at night in the local strains.

Schistosomiasis in brief. Cercariae released by infected snails penetrate intact skin in fresh water. Eggs lodge in the liver and intestine, causing chronic diarrhea, hepatosplenomegaly, portal hypertension, ascites, and variceal bleeding. Humans and animals (such as carabao, dogs, pigs, and rats) pass eggs in feces, which is why sanitation and snail control matter as much as treatment.

Levels of prevention applied

DOH "4S" strategy against dengue

1. Search and destroy mosquito breeding places — empty, scrub, cover, or discard water-holding containers (the "4 o'clock habit": do it every afternoon, at least weekly, because the mosquito life cycle from egg to adult is about a week).
2. Secure self-protection — long sleeves and pants, repellent, screens, bed nets for day sleepers.
3. Seek early consultation — for fever of 2 days or more, or any warning sign.
4. Support fogging or spraying — only in hotspot areas where cases are increasing (for example, rising for two consecutive weeks) to prevent an impending outbreak. Fogging kills adult mosquitoes only and is not a substitute for removing breeding sites.

Mass drug administration (MDA) treats a whole at-risk population regardless of individual test results. It interrupts transmission only when coverage is high (WHO: at least 65% of the total population for filariasis; the schistosomiasis program targets at least 85% of the eligible population).

• Filariasis: diethylcarbamazine (DEC) plus albendazole once a year for at least 5 years in endemic areas, until transmission assessment surveys (TAS) show infection below the WHO threshold.
• Schistosomiasis: praziquantel MDA for residents of endemic areas (the DOH program targets ages 5 to 65).
• Soil-transmitted helminths: school and community deworming with albendazole or mebendazole (see the school health topic).

Malaria elimination. The DOH aims for national malaria elimination by 2030. Its pillars are early diagnosis and complete treatment of every case, vector control with insecticide-treated nets and indoor residual spraying, case investigation and surveillance in malaria-free provinces (to catch imported cases), and preventing re-establishment.

Notifiable diseases. Dengue, malaria, filariasis, and schistosomiasis cases are reported through the national disease surveillance system under the notifiable diseases law (RA 11332, Mandatory Reporting of Notifiable Diseases and Health Events of Public Health Concern Act).

Dengue — community and clinic

• Diagnosis: CBC with platelets and hematocrit; NS1 antigen in the first days of fever; IgM/IgG serology later. The tourniquet test (inflate the cuff midway between systolic and diastolic pressure for 5 minutes; positive if 20 or more petechiae per 2.5 cm × 2.5 cm square) supports the diagnosis but is not specific.
• Home care for dengue without warning signs: rest; oral fluids and oral rehydration solution; paracetamol for fever (no more than the maximum daily dose); no aspirin, ibuprofen, or other NSAIDs (bleeding risk); daily review of fluid intake, urine output, and warning signs; return at once for any warning sign or when fever falls and the client feels worse.
• Hospital care: warning signs or severe dengue need IV isotonic crystalloid titrated to vital signs, hematocrit, and urine output; avoid fluid overload in the recovery phase.
• No dengue vaccine is part of the routine DOH program; check the current Philippine FDA registration status of any newer vaccine before advising clients.

Malaria

• Diagnosis before treatment: microscopy of thick and thin blood smears (species and parasite count) or a rapid diagnostic test (RDT) — ideally done by trained barangay microscopists or health workers in endemic areas.
• Treatment under the national protocol: artemether–lumefantrine plus a single low dose of primaquine for P. falciparum; chloroquine plus a 14-day course of primaquine for P. vivax (radical cure). Check G6PD status (it is included in newborn screening) before the 14-day primaquine course; primaquine is not given in pregnancy. Severe malaria needs IV artesunate in hospital.
• Prevention: long-lasting insecticide-treated nets used every night by everyone in the household; indoor residual spraying; clearing vegetation along streams; travelers to endemic areas use repellent and chemoprophylaxis as prescribed.

Filariasis

• Diagnosis: nocturnal blood examination (blood taken at night, when microfilariae circulate) or rapid antigen tests that can be done in the daytime.
• MDA day: give DEC and albendazole under direct observation after a meal; do not give DEC to pregnant women, children under 2 years, or the severely ill. Warn that fever, headache, and body aches can follow as microfilariae die; these are self-limited.
• Morbidity management: daily washing and careful drying of the affected limb (including between toes), skin and nail care, treating small wounds and fungal infections (entry points for bacteria), elevation and exercise of the limb, well-fitting footwear; referral for hydrocele surgery.

Schistosomiasis

• Diagnosis: stool examination (Kato-Katz) for eggs; ask about water contact in endemic barangays.
• Treatment: praziquantel 40 mg/kg as a single dose (split into two doses the same day if needed); take with food; swallow tablets whole; no driving or machine work on the day of treatment and the next day. WHO allows praziquantel in pregnancy after the first trimester.
• Prevention: build and use sanitary toilets (stops eggs from reaching water), avoid wading or bathing in infested water, wear rubber boots and gloves for farm work, clear canal vegetation and drain snail habitats, and treat or pen animal reservoirs where feasible.

1. Case finding and early referral — screen febrile clients for dengue warning signs first (this is the life-threatening priority); test suspected malaria cases the same day.
2. Treatment supervision — directly observe MDA doses and ensure completion of malaria regimens, including all 14 days of primaquine for vivax.
3. Surveillance and reporting — record and report notifiable cases on time; track cases on a spot map to find clusters and trigger barangay response.
4. Health education and community organizing — mobilize households, schools, and barangay officials for weekly cleanup drives; teach limb care and toilet use.
5. Coordination — work with the municipal health officer, sanitary inspector, barangay health workers, and the local government on vector control and environmental measures.
6. Program management — forecast drugs and RDTs, maintain nets and treatment records, and evaluate coverage against targets.

• Mandatory reporting of notifiable diseases (RA 11332) protects the community; report through official channels while keeping personal data confidential under the Data Privacy Act (RA 10173) — share only what the surveillance system requires.
• Informed participation in MDA: explain the purpose, expected side effects, and who should not take the drugs; respect refusal while correcting misinformation, and document it.
• Justice and equity: endemic diseases cluster in poor, remote communities; prioritize outreach, not only clinic-based services.
• Documentation: record drug doses, lot numbers, adverse events, and follow-up as for any medication administration.

Case 1. On day 4 of fever, a 12-year-old's temperature falls, but she has abdominal pain, vomiting, and cold hands. Her mother thinks she is recovering.

Action: Refer immediately to the hospital. Why: defervescence is the critical phase of dengue; abdominal pain and persistent vomiting are warning signs of plasma leakage and impending shock.

Case 2. During a filariasis MDA, a 25-year-old woman says she is 3 months pregnant.

Action: Do not give DEC now; record her and schedule treatment after delivery. Why: pregnancy is an exclusion for filariasis MDA drugs.

Case 3. A farmer from an endemic barangay in Leyte has chronic diarrhea and an enlarged abdomen.

Action: Arrange stool examination and referral; teach boots, toilet use, and avoiding infested water. Why: chronic S. japonicum infection causes hepatosplenic disease; prevention must address water contact and fecal contamination.

Case 4. A client from Palawan has a positive RDT for P. vivax.

Action: Confirm G6PD status before primaquine and ensure the full chloroquine and 14-day primaquine course. Why: primaquine clears liver forms (prevents relapse) but causes hemolysis in G6PD deficiency.

• Thinking dengue mosquitoes bite at night — Aedes bites in the daytime; malaria (Anopheles) bites at night.
• Treating fogging as the main dengue control — source reduction (removing breeding containers) is primary; fogging is reserved for hotspots.
• Giving aspirin or ibuprofen for dengue fever — use paracetamol only.
• Believing the client is safe when the fever breaks — the critical phase begins around defervescence.
• Stopping primaquine early for vivax — relapse follows.
• Taking filariasis blood films in the daytime — microfilariae of local strains are found at night (use antigen tests by day).
• Forgetting that schistosomiasis spreads through skin contact with fresh water, not by drinking water or mosquito bites.
• Thinking MDA is only for people with symptoms — it treats the entire eligible population.

• Dengue: Aedes aegypti, day-biting, clean stagnant water; phases febrile → critical (plasma leakage around defervescence) → recovery.
• Dengue warning signs: abdominal pain, persistent vomiting, fluid accumulation, mucosal bleeding, lethargy, liver enlargement, rising Hct with falling platelets.
• DOH 4S: Search and destroy, Secure self-protection, Seek early consultation, Support fogging only in hotspots.
• Dengue fever: paracetamol, no NSAIDs or aspirin, oral fluids; tourniquet test positive at 20 or more petechiae per 2.5 cm square.
• Malaria: Anopheles flavirostris, night-biting, foothill streams; Palawan carries most cases; elimination target 2030.
• Malaria diagnosis by blood smear or RDT; Pf = artemether–lumefantrine + single-dose primaquine; Pv = chloroquine + 14-day primaquine after G6PD check.
• Filariasis: DEC + albendazole annual MDA for at least 5 years; nocturnal blood exam; limb hygiene for lymphedema.
• Schistosomiasis: S. japonicum, snail Oncomelania hupensis quadrasi, skin contact with fresh water; praziquantel; sanitary toilets and boots.
• MDA works only with high coverage (filariasis: at least 65% of the total population per WHO; schistosomiasis program: at least 85% of those eligible).
• These diseases are notifiable under RA 11332.