The short version
- Among 17,212 patients on ships without a doctor assisted by Italy’s CIRM from 2011 to 2015, 146 had confirmed malaria, 21.79% of all infectious and parasitic disease cases[2].
- The same study found West African coasts carried the highest risk[2]. One P&I club reported two crew infected after a Congo port call; one died[3].
- Prophylaxis starts before arrival and continues after departure: from 1 to 2 days before and 7 days after, up to 2 weeks before and 4 weeks after, depending on the drug[1].
- Symptoms can appear as early as 7 days after exposure and as late as several months[1]. Fever after a risk-area call is malaria until a test says otherwise.
Malaria is still a working risk for crews, not a tourist problem
The most direct data comes from radio medical records. Pallotta and colleagues reviewed 17,212 health records of patients on ships assisted by CIRM, the Italian radio medical centre, from 2011 to 2015, in a study published in Acta Biomedica[2].
| Finding[2] | Figure |
|---|---|
| Confirmed malaria cases | 146 |
| Share of infectious and parasitic disease | 21.79% |
| Suspected, unconfirmed cases | 16 |
| Peak year | 35 confirmed in 2012 (41.67% of infectious diseases) |
| 2015 | 20 confirmed (12.99%) |
| Deaths in the series | 0 |
Zero deaths in that series is the good news, and it came with physicians on the radio. Outside it, the record is harsher: the American Club reported two crew members who contracted malaria after a port call in the Congo, one of whom died[3]. In the US, CDC notes almost all of the roughly 2,000 malaria cases a year are imported[1], which includes crew signing off from risk-area trades.
Where the risk sits on a trading route
The CIRM data placed the highest risk on the coasts of West Africa, with intermediate risk near the Middle East[2]. Risk is set per destination, so the prevention plan has to follow the route, not the vessel type.
P&I guidance groups destinations into four types, from mosquito bite prevention alone (Type I) up to bite prevention plus atovaquone-proguanil, doxycycline or mefloquine (Type IV)[3]. Use the current CDC Yellow Book country entry for the specific port before every risk-area voyage[1]; risk maps change.
Prophylaxis timing: the table the crew change plan needs
Each drug has its own start and stop rule. The stop rule is the one crews miss: protection continues after the ship leaves the risk area[1].
| Drug[1] | Start | Continue after leaving the risk area |
|---|---|---|
| Atovaquone-proguanil | 1 to 2 days before | Daily for 7 days |
| Doxycycline | 1 to 2 days before | Daily for 4 weeks |
| Mefloquine | At least 2 weeks before | Weekly for 4 weeks |
| Tafenoquine | 3 days before | One 200 mg dose in the week after leaving |
| Primaquine | 1 to 2 days before | Daily for 7 days |
| Chloroquine | 1 to 2 weeks before | Weekly for 4 weeks |
The drug choice is a prescribing decision for a physician who knows the destination and the crew member’s history. Two operational points follow from the table: a relief crew member flying in on short notice may only fit the 1 to 2 day options, and a crew member signing off two days after the last risk-area call still has up to four weeks of tablets to take ashore[1]. Their own supply then crosses borders as personal medication; see seafarer prescription medication rules.
Long voyages change the plan
CDC treats travelers away 6 months or more as a separate group: buy enough medication before departure, keep adherence, plan for illness and consider a standby treatment supply[1]. A deep-sea rotation fits that description better than a tourist itinerary does.
Keeping mosquitoes off the ship
Drugs reduce risk; bites cause it. The American Club’s precautions apply within about 2 miles of a malarious shore[3]:
- Close doors and windows after dusk[3].
- Long sleeves and trousers on deck after dark[3].
- Insect spray in compartments[3].
- Fine wire mesh on portholes and ventilation openings[3].
- Air conditioning running continuously[3].
- Impregnated mosquito nets, tucked under mattresses[3].
Ports apply their own rules too. Under IHR Annex 5, ships leaving an area where vector control is recommended should be disinsected, with the measures recorded on the Ship Sanitation Control Certificate[4]. See the ship sanitation certificate guide and, for the related crew certificate, yellow fever certificates for ship crew.
Standby treatment in the medicine chest
CDC names two regimens available in the US that can be prescribed as a reliable supply for self-treatment: atovaquone-proguanil and artemether-lumefantrine[1]. P&I guidance ties standby treatment to fever starting a week or more after entering a risk area[3], matching CDC’s earliest symptom window of 7 days[1].
No US federal rule sets the contents of a ship’s chest; FDA has never recommended a particular procedure for supplying one[5]. That leaves the antimalarial stock to the operator and the prescribing physician. Size it to crew and route with how to stock a ship medicine chest, check flag lists in ship medicine chest requirements by flag state, and decide in advance when a febrile crew member comes off the ship: when to medevac a seafarer.
Pre-voyage malaria checklist
| Check | Source |
|---|---|
| Every risk-area port checked against the current CDC country entry | CDC Yellow Book[1] |
| Prophylaxis prescribed and started to the drug’s start rule | CDC Yellow Book[1] |
| Enough tablets to finish the post-departure course | CDC Yellow Book[1] |
| Mosquito precautions briefed for the 2-mile zone | American Club[3] |
| Standby treatment in the chest, in date | CDC Yellow Book[1] |
| Sign-off briefing: report fever and travel history for months after | CDC Yellow Book[1] |
Discovery Health MD turns this into a route-specific plan: a physician-written prophylaxis and fever protocol through maritime medical consulting, standby treatment stocked and dated through ship medical chest management, and the controlled items in the same chest through controlled substances management. Send us the ports on your next West Africa run.
Common questions
Do seafarers need malaria prophylaxis?
When the route includes malaria risk areas, yes, as prescribed for the destination[1]. Ship radio medical data recorded 146 confirmed cases in five years, over a fifth of infectious disease cases[2].
Which areas carry the highest malaria risk for ships?
The CIRM study found the coasts of West Africa carried the highest risk, with intermediate risk near the Middle East[2]. Check each port in the CDC Yellow Book[1].
How long before arriving should crew start antimalarials?
It depends on the drug: 1 to 2 days for atovaquone-proguanil, doxycycline or primaquine, 3 days for tafenoquine, 1 to 2 weeks for chloroquine and at least 2 weeks for mefloquine[1].
How long after leaving should crew keep taking them?
From 7 days (atovaquone-proguanil, primaquine) to 4 weeks (doxycycline, mefloquine, chloroquine); tafenoquine needs one dose in the week after[1].
What should be in the medicine chest for malaria?
CDC lists atovaquone-proguanil and artemether-lumefantrine as US-available standby treatment regimens[1]. No US federal contents list exists[5], so the prescribing physician sets quantities.
How soon can malaria symptoms start?
As early as 7 days after exposure and as late as several months or more[1]. A fever in that window needs a malaria test and medical advice; see medical emergencies at sea.
How do you keep mosquitoes off a ship?
Within about 2 miles of a malarious shore: close up after dusk, cover skin, spray compartments, screen portholes and vents, run air conditioning and use impregnated nets[3].
