Vector-borne diseases represent a significant public health challenge. They account for more than 17% of all infectious diseases worldwide and cause over 700,000 deaths annually. These diseases are transmitted through the bites of infected mosquitoes, ticks, sand flies, and other vectors, and can be caused by viruses, bacteria, or parasites.

Climate change, environmental changes, increased travel, and trade contribute to the spread of vectors into new areas and extend the period during which they remain active. As a result, the risk of occurrence and spread of vector-borne diseases is increasing.

In Macedonia, diseases such as Lyme disease, West Nile virus infection, hemorrhagic fevers, leishmaniasis, and tularemia are registered, while malaria, dengue, Zika, and chikungunya represent a potential risk for introduction and local transmission through the vectors present in the country.

MOSQUITO-BORNE DISEASES

West Nile Fever (West Nile Virus Infection)

West Nile fever is a viral disease most commonly transmitted through the bite of an infected mosquito of the genus Culex. Birds are the natural reservoir of the virus, while humans and horses are accidental hosts. The virus is not transmitted from person to person through ordinary contact.

Around 80% of infected individuals do not develop symptoms. Approximately 20% develop a mild form of the disease (West Nile fever), while less than 1% may develop a severe neuroinvasive form (meningitis, encephalitis, or acute flaccid paralysis), particularly older adults over 60 years of age and people with weakened immune systems.

In Macedonia, laboratory-confirmed cases of West Nile virus infection are occasionally registered, most commonly during the summer and autumn months when mosquito activity is highest. Circulation of the virus has been confirmed in the country, which is why continuous epidemiological and laboratory surveillance is carried out.

The most common symptoms of infection include: fever accompanied by chills, headache, body and muscle aches, fatigue and weakness, nausea and vomiting, and rash. The appearance of severe headache, stiff neck, altered consciousness or confusion, or weakness of the limbs may indicate possible neurological complications requiring urgent medical attention.

Dengue

Dengue is a viral disease transmitted through the bite of an infected mosquito of the genus Aedes, most commonly Aedes aegypti and Aedes albopictus (the Asian tiger mosquito). Unlike West Nile virus infection, where humans are accidental hosts, in dengue infection humans are the main reservoir and source of infection in urban areas.

The disease is not transmitted from person to person through ordinary contact; however, an infected person during the period when the virus is present in the blood can serve as a source of infection for mosquitoes. In this way, the transmission cycle between humans and mosquitoes is maintained, allowing rapid spread of the disease and the occurrence of local outbreaks.

Most people recover within 1–2 weeks. However, a small proportion of patients may develop severe dengue, characterized by bleeding, organ damage, and shock, conditions that can be life-threatening if not recognized and treated promptly.

In Macedonia, local transmission of dengue has not been registered so far. Imported cases are occasionally reported among persons who have stayed in countries where the disease is endemic.

The most common symptoms are: high fever, severe headache, intense muscle and joint pain, pain behind the eyes, nausea and vomiting, and skin rash.

 Zika

Zika is a viral disease transmitted through the bite of an infected mosquito of the genus Aedes. As with dengue, humans are the main reservoir and source of infection in urban areas. The disease is not transmitted through ordinary person-to-person contact; however, in addition to mosquito bites, the virus can also be transmitted from mother to fetus during pregnancy, through sexual contact, and, very rarely, through blood transfusion.

An infected person during the period when the virus is present in the blood can serve as a source of infection for mosquitoes, thereby allowing continuation of the transmission cycle.

Most infected people (around 80%) have no symptoms or develop a mild form of the disease. However, infection during pregnancy can cause serious congenital abnormalities in the fetus, including congenital Zika syndrome and microcephaly.

In Macedonia, local transmission of Zika virus has not been registered so far, and one imported case has been reported. Due to the presence of the Asian tiger mosquito (Aedes albopictus) in the country, there is a potential risk of local transmission if conditions for virus circulation are met.

The most common symptoms are: mild fever, skin rash, redness of the eyes (conjunctivitis), headache, and muscle and joint pain.

Chikungunya

Chikungunya is a viral disease transmitted through the bite of an infected mosquito of the genus Aedes, the same mosquito genus that transmits dengue and Zika.

The disease is characterized by sudden onset of fever and severe joint pain, which in some patients may last for weeks or months. Most infected individuals recover completely, but prolonged joint pain may persist in some cases.

Severe forms of the disease are rare; however, newborns, older adults, and people with chronic diseases have a higher risk of complications.

In Macedonia, local transmission of chikungunya has not been registered so far, and one imported case has been reported. Due to the presence of the Asian tiger mosquito (Aedes albopictus) in the country, there is a potential risk of local transmission if an infected person is bitten by a competent vector.

The most common symptoms of infection are: high fever, severe joint pain, muscle pain, skin rash, fatigue, and headache.

Malaria

Malaria is a parasitic disease caused by parasites of the genus Plasmodium, transmitted through the bite of an infected female mosquito of the genus Anopheles.

Unlike viral mosquito-borne diseases, malaria is caused by a parasite and, without timely treatment, can lead to severe complications and death.

The highest risk of severe disease occurs among young children, pregnant women, older adults, and people with weakened immune systems. The most severe clinical form is caused by Plasmodium falciparum, which is responsible for the majority of malaria-related deaths worldwide.

In Macedonia, malaria has been eliminated as an autochthonous disease and there is no local transmission. Imported cases are occasionally reported among people who have travelled to endemic areas, most commonly countries in Sub-Saharan Africa, Asia, and South America.

The most common symptoms of malaria are: high fever accompanied by chills, excessive sweating, headache, nausea, vomiting, and severe fatigue and weakness.

How to Protect Yourself from Mosquitoes?

Environmental measures

Prevent mosquito breeding in your surroundings:

·         Do not leave open barrels, containers, boats (canoes, small boats), or old tires in yards where rainwater can accumulate.

·         Clean gutters regularly to allow proper drainage of water.

·         Keep swimming pools, decorative pools, and fountains clean.

Reduce exposure to mosquito bites:

·         Use scented candles, mosquito coils, and other repellent products when staying outdoors in gardens or yards.

·         Use mosquito-repelling or mosquito-control devices that use light or ultrasound.

·         Install protective screens on doors and windows.

·         Avoid going outdoors and staying outside from sunset until dawn, when mosquitoes are most active.

Personal protection measures against mosquito bites

·         Wear light-colored, long clothing that covers the arms and legs and leaves as little exposed skin as possible (long sleeves, long trousers, socks, hats).

·         Use protective repellents in the form of lotions, sticks, aerosol sprays, or creams for skin and clothing that repel mosquitoes.

Protection Measures When Traveling to Endemic Areas

·         Follow travel health recommendations issued by local health authorities.

·         Get vaccinated against diseases for which vaccination is recommended and available, such as yellow fever.

·         Use preventive medication, such as antimalarial prophylaxis, before and during travel according to medical advice.

·         When travelling to or staying in endemic countries, always use repellents and keep windows and sleeping areas protected with insecticide-treated nets.

·         After returning from travel, monitor your health and seek medical advice immediately if symptoms appear, informing healthcare providers about travel history to endemic areas.

Lyme Disease (Lyme Borreliosis)

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, which is transmitted through the bite of an infected tick of the genus Ixodes. The risk of transmission increases if the tick remains attached to the skin for a longer period of time. The disease can be treated with antibiotic therapy; therefore, early diagnosis is important.

In Macedonia, Lyme disease is the most commonly reported tick-borne disease. Cases are reported every year, most frequently during spring and summer when tick activity is highest.

The most common symptoms of Lyme disease are: a circular redness at the site of the bite that gradually expands (erythema migrans), fever, headache, muscle and joint pain, and fatigue.

Crimean-Congo Hemorrhagic Fever (CCHF)

Crimean-Congo hemorrhagic fever is a severe viral disease most commonly transmitted through the bite of an infected tick of the genus Hyalomma or through contact with blood and tissues of infected animals.

It can also be transmitted through direct contact with blood or body fluids of an infected person, especially in healthcare settings where appropriate protective measures are not applied.

In Macedonia, sporadic cases are occasionally registered, mainly in the eastern and northeastern regions of the country. Although the disease is rare, its high mortality rate requires rapid recognition and urgent treatment.

The most common symptoms include: sudden onset of fever, severe headache, muscle and joint pain, nausea, vomiting, abdominal pain, and pronounced weakness.

Urgent medical attention is required if, after a tick bite, the following symptoms appear:

• bleeding from the nose or gums;
• bruising on the body;
• blood in vomit or stool;

Recommendations for Tick Bite Prevention

Preventing tick bites:

• Avoid staying in areas where ticks are common (tall grass, bushes, forests).
• Wear light-colored clothing with long sleeves and long trousers, covering arms, legs, neck, and head as much as possible.
• Treat clothing with sprays containing synthetic pyrethroids, such as permethrin, or use commercially available permethrin-treated clothing to reduce the possibility of ticks attaching to clothing. Do not apply permethrin products directly to exposed skin.
• When working with animals, use protective equipment and avoid direct contact with blood and tissues of potentially infected animals.
• Additional protection can be provided by tick and insect repellents containing diethyltoluamide (DEET), which may be applied to exposed skin according to instructions.

After Spending Time in Nature

• Check clothing for ticks. Ticks can be brought into the home on clothing. Remove any ticks found.
• Dry clothes in a dryer at high temperature for 10 minutes to kill ticks on dry clothing. If washing is needed first, use hot water. Cold or medium-temperature water may not kill ticks.
• Check pets for attached ticks.
• Shower soon after returning from outdoor areas. Showering may help remove unattached ticks and provides an opportunity to check the body.
• Perform a full-body check after returning from areas where ticks may be present, including your yard. Use a mirror to examine hard-to-see areas.

Ticks are commonly found attached:

• under the arms;
• around the groin area;
• around the ears;
• inside the navel;
• in the hair;
• between the legs;
• around the abdomen.

DISEASES TRANSMITTED BY SAND FLIES

Cutaneous Leishmaniasis

Cutaneous leishmaniasis is a parasitic disease caused by parasites of the genus Leishmania, transmitted through the bite of an infected sand fly (Phlebotomus).

The disease affects the skin and subcutaneous tissue and is usually not life-threatening; however, it may leave permanent scars if untreated.

In Macedonia, cutaneous leishmaniasis is rarely reported. Nevertheless, due to the presence of sand flies in the region and the occurrence of the disease in neighboring and Mediterranean countries, continuous surveillance and timely recognition of suspected cases are important.

The most common symptoms of cutaneous leishmaniasis are:

• painless nodular skin lesions;
• skin ulcers that heal slowly;
• one or multiple skin lesions;
• locally enlarged lymph nodes.

Visceral Leishmaniasis (Kala-azar)

Visceral leishmaniasis is a severe parasitic disease caused by parasites of the genus Leishmania, transmitted through the bite of an infected sand fly (Phlebotomus).

The parasite affects internal organs, most commonly the spleen, liver, and bone marrow. Without timely treatment, the disease can be fatal.

In North Macedonia, visceral leishmaniasis occurs sporadically and represents an endemic zoonotic disease in certain areas. Dogs are the main reservoir of the parasite; therefore, animal surveillance plays an important role in disease control.

The most common symptoms of visceral leishmaniasis include:

• prolonged or recurrent fever;
• severe weakness and weight loss;
• enlarged spleen and liver;
• pale skin due to anemia;
• night sweats.

Early diagnosis and timely treatment are essential for successful recovery.

Recommendations for Protection Against Sand Flies

The most important preventive measure is protection against sand fly bites. When staying in areas where the disease is present, it is recommended to:

• use repellents on exposed areas of skin;
• wear long-sleeved clothing and long trousers, especially from dusk until dawn when sand flies are most active;
• stay in rooms with protective screens on windows and doors or sleep under insecticide-treated bed nets;
• reduce areas around homes that are suitable for sand fly breeding.

Because dogs are the main reservoir of the parasite, regular veterinary checks and the use of protective products against sand flies in dogs play an important role in reducing the risk of disease transmission.