The sandfly species present in New Zealand are a public health nuisance, however, they are not a public health risk, as the species that bite do not carry any infectious or transmittable diseases.
Sandflies, worldwide termed blackflies (Simuliidae), or alternatively namu in Māori, are common insects in New Zealand.
Types of sandfly
While there are 19 sandfly species found in New Zealand, only 3 of these bite humans:
- the New Zealand blackfly (Austrosimulium australense), found in the North Island and coastal areas of the South Island
- the West Coast blackfly (A. ungulatum), found in the South Island only
- A. tillyardianum, found on both islands, although not in great numbers.
These 3 species are very similar in size (approximately 2–3mm in length) and appear identical to the naked eye.
Where are sandflies found?
Sandflies breed in running water and are particularly prolific in areas near water and humid bush, for example at beaches, lakes, rivers and swamps.
They are daybiters, striking primarily at dawn and dusk.
Sandflies are renowned for their bite, however it is only the female sandfly that bites as she requires blood to produce eggs and acquires this by piercing the skin. The subsequent itchiness, redness and swelling that these bites cause should not warrant huge concern.
While overseas species are recorded to carry and transfer diseases, New Zealand species do not.
Reactions will vary between people, and visitors to New Zealand who have not previously been exposed to sandflies seem to react more severely than locals.
The effects of sandfly bites can be present for any period ranging from a few days to several weeks depending on the severity of the reaction.
Treatments for sandfly bites vary. It is most common to apply an antihistamine cream or calamine lotion to soothe the affected areas, or for a severe reaction an antihistamine pill may be required.
If bitten, you should refrain from scratching the bites as the risk of secondary infection will escalate should the skin be broken.
The following precautions may be taken to prevent being bitten.
- Cover up when stationary, particularly ankles and feet.
- Apply an insect repellent regularly when exposed to sandflies (those containing diethyl toluamide or dimethyl phthalate as the active ingredients are most effective).
- Burning a citronella candle will also help in a small area to deter sandflies.
- Taking additional Vitamin B may also help your immunity to reaction.