Introduction:
Vector-borne (carriers of disease) infections are a common global health concern. Approximately more than 0.5 million people die annually due to vector-borne diseases. Most vector-borne diseases occur in subtropical and tropical countries like Africa, India, Brazil, China, etc. These diseases are transmitted by insects like mosquitoes, ticks, and sandflies. While Lyme disease, malaria, and dengue are common, diseases like West Nile fever, yellow fever, and sandfly fever occur less frequently. These vectors carry pathogens like viruses, parasites, and bacteria. Vector-borne diseases are seasonal and cause endemic (diseases that occur in a particular area) outbreaks. One such disease caused by a sandfly bite is sandfly fever.
What Are Sandflies?
Sandflies are blood-sucking, biting, flying insects found mostly in sandy regions of central Asia, the Mediterranean coast, and southern and central America. Sandflies are known to carry viruses like Chandipura virus, Bunyavirus, and parasites like Leishmania. One such virus, the Phlebovirus (belongs to the Bunyavirus group from the arbovirus family), causes sandfly fever. The sandfly fever virus (Phlebovirus species) is an RNA virus. Four subtypes of the sandfly fever virus have been identified: Naples, Sicilian, Toscana, and Cyprus.
What Is Sandfly Fever?
The sandfly fever is known by other names, such as phlebotomus fever, three-day fever, and pappataci fever. It is a self-limiting, non-fatal fever transmitted by the bite of an infected sandfly, Phlebotomus papatasi. The transmission cycle occurs from April to October (warm seasons). An adult female sandfly is known to bite humans, causing the infection. Sandflies can easily pass through mosquito nets.
How Does a Person Catch Sandfly Fever?
The disease follows an animal or human-vector-human transmission. After breeding in the summer season, the sandfly can become infected after biting the host (including warm and cold-blooded vertebrates and plants). The pathogens from an infected human can also be transmitted to the sandfly. This transmission happens anytime before one to two days of onset of symptoms. The insects act as a reservoir and carriers of the virus. It remains inside the sandfly for life after an incubation period of seven to 10 days. Once the sandfly bites another human, the virus is transferred to the healthy individual.
What Happens After an Infected Sandfly Bites a Healthy Human?
After the bite, a rash or papule (raised area on the skin) is formed at the site. The virus spreads throughout the body of a healthy individual within one week. The virus incubation period inside the human host lasts for a few days up to two weeks. The infected individuals experience discomfort after two to five days of exposure. After the incubation period, the symptoms start to appear.
What Are the Symptoms of Sandfly Fever?
The symptoms of sandfly fever are usually self-limiting (the disease resolves without any treatment). The most common symptoms include:
A. General Symptoms - Fatigue, weakness, abdominal distress, loss of appetite, dizziness, etc.
B. Fever - Within two days, a rapid rise in body temperature is observed. The temperature rises to 102 to 104 degrees Fahrenheit. The fever and chills last for two to three days before it starts to subside.
C. Pain - Patients experience intense pain in muscles, joints, around the eyes (periorbital), and abdomen. Severe headache in the frontal region is common.
D. Skin - The face can appear flushed; scales and rashes are uncommon.
E. Other Symptoms - Sometimes, the patients can experience redness in the eyes (due to increased blood flow) and photosensitivity.
F. Pulse - Patients experience palpitations and high pulse rates during the initial days.
After the febrile episode, some patients continue to experience weakness and may also see a rise in the temperature (second episode). Patients may also have a slow pulse rate and fluctuating blood pressure. Although it takes a few days to several weeks for the symptoms to completely subside, the patients show excellent recovery.
Can Sandfly Fever Cause Meningitis?
Yes, a subtype of the Phlebovirus known as the Toscana virus is known to cause meningitis (inflammation of protective layers of the brain). According to studies and case reports, 80 % of the summer cases of non-bacterial meningitis (in endemic areas) are caused by this virus. The patients experience symptoms like fever, headache, vomiting, and rigidity in the neck. Other neurologic symptoms of peripheral neuropathy like numbness, weakness, and pain in the hands and feet are also seen. The Turkey subtype of the Phlebovirus can also cause severe disease.
How Severe Is Sandfly Fever?
Although some subtypes of the virus can cause severe disease, the condition is often mild to moderate. The disease resolves by itself within a few days to weeks. According to studies, no cases of mortality (death) have been reported so far.
How Is Sandfly Fever Diagnosed?
Just by studying the clinical symptoms, the clinicians cannot confirm the diagnosis of sandfly fever. The diagnosis can be made after correlating the clinical symptoms and laboratory test reports and by studying the epidemiological information. Other viral infections should be ruled out after relevant tests. Various laboratory tests that need to be performed include:
1. CBC (Complete Blood Count) - The striking feature of this disease includes:
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Leukopenia and lymphopenia (decrease in leukocytes and lymphocytes, a type of white blood cells).
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Monocytosis (increased monocytes, a type of white blood cells).
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Thrombocytopenia (decrease in platelets).
2. Liver and Kidney Function Tests - These tests show an increase from the normal value.
3. Serologic Test - It comes positive for IgM or IgG antibodies.
4. RT-PCR (Reverse Transcription-Polymerase Chain Reaction) - It is used to detect the sandfly fever RNA virus.
5. Viral Isolation - Viral isolation from blood or CSF (cerebrospinal fluid) can be done to confirm the diagnosis.
Is Sandfly Fever Contagious?
No, sandfly fever does not directly spread from an infected human to a healthy human. Instead, a bite from an infected sandfly is necessary to transmit the disease.
What Is the Treatment for Sandfly Fever?
The treatment for sandfly fever is symptomatic. There is no specific drug available to destroy the virus. Supportive treatments like analgesics, antibiotics, bed rest, and fluid therapy are given to the patients until the symptoms resolve.
Can Sandfly Fever Be Prevented?
Since the breeding places of sandflies are challenging to find, the WHO (World Health Organization) has come up with guidelines to prevent the outbreak of vector-borne diseases.
The following steps can be followed to avoid being bitten by a sandfly.
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Avoid traveling to the endemic areas during summer.
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Wear light-colored clothes that fully cover the body.
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Use insect repellent creams, window shields, and mosquito nets.
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Regularly check your body for bites.
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Use insecticide sprays on screens, windows, and doors.
Conclusion:
Sandfly fever is caused after getting bit by an adult female sandfly infected with Phlebovirus. It is a self-limiting disease that resolves after a few days. The most common symptoms include fever, headache, flushing, vomiting, joint pain, and weakness. Diagnosis is confirmed after specific lab tests and studying epidemiological data. Treatment usually involves supportive therapy. The infection is not contagious and can be prevented by taking safety measures. Vector-borne diseases are a global threat. Therefore, it is necessary to take specific steps to prevent such outbreaks.
