Only seen leeches - never had a problem and I do lots of jungle treking.
Insect repellent (to keep them off) is most effective - leech socks are not much good for the neck !!! Tea Tree oil will help.
DO NOT use insect repellent or salt to remove them as they will vomit into the wound and cause infection.
This may help you:
How to Remove a Leech
1. Do not attempt to remove a leech by pulling up on its middle section or by using salt, heat, or insect repellent. Dislodging by squeezing, salting, burning, or otherwise annoying the leech while it is feeding will cause it to regurgitate, most likely spreading the bacteria from its digestive system into your open wound, causing infection.
2. Identify the anterior (oral) sucker. Look for the small end of the leech. A common mistake is to go immediately to the large sucker.
3. Place a fingernail on your skin (not on the leech itself), directly adjacent to the oral sucker.
4. Gently but firmly slide your finger toward where the leech is feeding and push the sucker away sideways. When the seal made by the oral sucker is broken, the leech will stop feeding. After the oral sucker has been dislodged, the leech’s head will seek to reattach, and it may quickly attach to the finger that displaced the head. Even if the oral sucker attaches again, the leech does not begin to feed immediately.
5. Displace the posterior (hind) sucker. While continuing to flick occasionally at the small end, push at or pick under the large end (hind sucker) with a fingernail to cause it to lose its suction.
6. Dispose of the leech. At this point, the leech may have securely attached itself to the finger you used to remove it. Flick it off—it should detach easily. Once the leech is detached, you can put salt or insect repellent directly on it to keep it from attaching to anything else.
7. Treat the wound. After the leech’s anticoagulants lose their effect, the wound should heal quickly. Keep the area clean, and cover it with a small bandage if necessary. Avoid scratching the wound. If itching becomes severe, take an antihistamine.
If a Leech Invades an Air Passage
Hirudiniasis is a potentially serious condition in which one or more leeches invade a body orifice. In particular, Dinobdella ferox (literally, “the terrifying ferocious leech” or “nasal leech”) has a predilection for airways, where it may cause a blockage or asphyxiation, especially if leeches invade the passage in large numbers. If there is a leech invading your airway and you can breath, do not attempt to remove it—seek medical attention immediately. If you cannot breathe, take the following steps:
1. Gargle with diluted 80-proof alcohol. Most distilled liquors—vodka, gin, bourbon, scotch—have the requisite alcohol content. Use a mixture of 50 percent alcohol, 50 percent water. Be careful not to aspirate (inhaling the leech and the alcohol).
2. Spit out the leech.
If gargling does not work and the leech is visible, remove it by grasping firmly at the hind sucker and yanking.
* There is virtually no risk of substantial blood loss from leech bites. The wound will continue to bleed for some time after a leech has finished feeding, but this level of blood loss is not dangerous.
* Leeches are generally not known to transmit blood parasites to humans.
* Leeches are more likely to be encountered in still water than in rivers or streams. They are more often found near the edges of clean, clear water than in or near swamps.
* Leeches need a solid surface to hold on to even when they are not feeding. Avoid leeches by staying in the open: Swim in deep, open water, avoid boat docks, and do not wade through areas with submerged branches or rocks. In jungles, remain on trails and be aware of leeches on overhanging branches and vines.
* Both aquatic and terrestrial leeches have incredible senses of perception. They are attracted by vibrations and by body heat, and they have 10 pairs of eyes to detect movement. Keep moving, and check yourself and your traveling companions regularly.