There are two parasites that can infect dogs through their skin, when dogs come into contact with their larvae in soil. The first-stage larvae burrow through the dog’s skin and develop into later-stage larvae, and, eventually into a botfly, which lays its eggs in soil.
Mango worms
The mango worm the larvae of the African tumbu fly. After getting through the dog’s skin, the larva creates a small furuncle that looks like a pimple. The furuncle has a small opening through which the larva breathes.
Once inside the skin, the larva molts into a second stage larva and then a third stage larva. The second stage larva is shaped like a club and is 2.5 to 4.0 millimeters long (about ⅛ of an inch). The third stage larva is shaped like a cylinder and is about 1.5 centimeters long (about ½ of an inch). The initial furuncle may be itchy for a couple of days and then subside. As the larva grows and matures, the furuncle may develop into a painful boil with a weeping discharge. Once the larva has reached maturity, it leaves the boil to finish pupating into the tumbu fly.
Mango worms are endemic in the sub-Saharan region of Africa. Infection with this larva is rarely seen in the United States. When infection with mango worms is seen in the United States, it is typically associated with recent travel to Africa. So, unless your dog is a world traveler, you don’t need to worry about mango worms!
Cuterebra
Cuterebra is the larva of the rabbit botfly. This larva also burrows into the skin and initially creates a small swelling about one centimeter wide. As the larva grows and matures, the swelling can become large and painful and look like an abscess. The swelling will have a small hole in the middle through which the larva breathes. If you look carefully at the hole, you may see the larva moving inside!
Unlike the mango worm, cuterebra is found throughout the United States. Immature larvae are grey or cream-colored, shaped like a cylinder with little ridges, and 0.5 to 1 centimeter long (about ¼ to ½ inch). The mature larvae are dark grey, can be up to three centimeters long (about 1 ¼ inches) and are cylindrically shaped with many ridges and spines.
