Usually before going to the tropics everyone warns me to avoid mosquitoes; however, there is another villainous insect of note that plagues my days in the tropics… sandflies.
What are sandflies, you ask? “Sandfly” is the common name for a group of blood feeding flies that leave a nasty, itchy bite in their wake (I hate sandflies). Sandflies occur all around the world and have many names. Back in California, I had heard the terms biting midge and noseeum in reference to these tiny, biting machines, but they can also be called a sand gnat, sandflea, chitra, and my personal favorite, granny nipper. I would love to know where in the world people call these flies granny nippers. Sandflies are from the Psychodidae family and the Phlebotominae subfamily, which contains more than 600 species.
Phlebotominae sand flies are very small, usually smaller than 3 mm. They have a diverse range of colors from white to a dark brown that appears black. They have three easily recognizable characteristics: 1) While standing still, they keep their wings at an angle above their abdomen 2) They are hairy (and even have hair along their wings!) and 3) They will typically hop around on their victim before settling on a place to bite. Another fun fact about sandflies is that they are weak fliers, having a maximum flight speed in wind tunnel tests of 1 m/sec!
Sandfly bites are easily characterized by a red dot in the middle of the bite site. They often swell up more than mosquito bites, itch more, and take longer to heal. Lucky for me, they LOVE me. They eat me alive where I’m standing (I hate sandflies). Sandfly bites are often worse than mosquito bites because of the morphology of their mouthparts. Unlike mosquitoes, who have elegant, straw-like mouthparts that cleanly pierce your skin, sandflies have saw-like mouthparts, which the female sandflies use to cut at your skin until a little pool of blood forms. Then the fly laps up the blood from the pool on the victim’s skin. The sawing action of their bite causes more skin irritation than a piercing mouth part, so these bites are itchier and take longer to heal (I hate sandflies). In addition, the sandfly injects saliva as she bites to prevent the blood from clotting, and this saliva can cause an allergic reaction in some hosts. This saliva is also an immunosuppressant, which can cause an increased frequency of infection at the bite site (I hate sandflies).
What’s even worse, sandflies can spread the disease leishmaniasis (also called tropical sore and sandfly fever). Only phlebotomine flies can spread leishmaniasis, specifically the genera Phlebotomus in the Old World and Lutzomyia in the New World. Leishmaniasis is a disease caused by a protozoa called Leishmania spp. that causes cutaneous lesions on your skin. Leishmania is a heteroxenous parasite, meaning that their life cycle requires two hosts. In this case, a sandfly and you or your dog. There is another version of leishmaniasis that eats away at cartilage, often found in your nose (I hate sandflies). There is also visceral leishmaniasis, which can be fatal, that affects your internal organs such as your liver, spleen, and bone marrow. I know you may be tempted to google a photo of a leishmaniasis infection, but you shouldn’t (You really shouldn’t). Before you never sleep again, remember that leishmaniasis is treatable, although relapses are an issue, so go to your doctor if you see any wounds on your skin that do not heal and always mention that you have been in the tropics.
Did I mention that I hate sandflies?
Killick-Kendrick, R. (1999) The Biology and Control of Phlebotomine Sand Flies. Clinics in Dermatology. 17: 279-289.
Gramiccia, M. Gradoni, L. (2005) The current status of zoonotic leishmaniases and approaches to disease control. International Journal for Parasitology. 35: 1169-1180.
“Morphology and Life Cycle.” UCLA. http://dna.kdna.ucla.edu/parasite_course-old/leish_files/subchapters/Morphology%20and%20Life%20cycle.htm. Accessed 5 February 2017.
“Parasites – Leishmaniasis.” Centers for Disease Control and Prevention. January 10, 2013. https://www.cdc.gov/parasites/leishmaniasis/. Accessed 5 February 2017.
Photo from “Entomology Louse, Bedbugs & Sand fly.” http://www.slideshare.net/jamesmacroony/entomology-louse-bedbugs. Accessed 5 February 2017.