Cuterebra Infestation in Cats

Often, the cat will ingest the larvae while grooming itself. Migrating larvae can, on rare occasions, travel through the eye, brain or spinal cord. This is a life-threatening scenario which can cause great damage to the cat. Once the larva has reached a chosen location, usually just under the skin, it forms a cavity with a small breathing hole to the outside air to further its development. At this stage, the larvae is commonly referred to as a warble. It can take one to two months for the warble to complete its growth and exit the cat via the hole in the cavity. 

A Cuterebra fly is a large, fat bot fly found throughout the United States. There are 34 species of Cuterebra in North America. The fly itself does not bite, however, its larvae need live hosts to develop. The female fly lays her eggs near rodent burrows and on runways used by rabbits. The eggs attach to an animal's coat when rubbed against. Upon feeling the heat of a live host, the eggs will hatch immediately and travel to any opening on the body. This can include the mouth, nose or an open wound on an animal. Once inside, the larvae travel through the body to specific locations on the head, neck or body. While rodents are the preferred host of the Cuterebra larvae, cats can be accidentally infested.

Presence of a warble may be more difficult to notice in cats with long hair. Sometimes the cavities may be deep and produce more severe symptoms. If symptoms occur rapidly, a life-threatening situation may be at hand and immediate veterinary attention is required. Known signs of Cuterebra infestation are as follows:

• Small bulge or swelling approximately 1cm in diameter on cat's skin
• Area of matted fur
• A wound of unknown origin
• Lesional discharge
• Excessive grooming
• Upper respiratory infection
• Violent sneezing
• Pain
• Depression
• Lethargy
• Head tilting
• Circling
• Seizures
• High body temperature

Any cat who is allowed outdoors is at risk of coming into contact with Cuterebra bot fly eggs. The summer and fall are more prevalent exposure times in climates with a true winter. All known causes are listed below.

• Hunting rodents
• Roaming through infested vegetation
• Having an open wound
• Resting in one outdoor area for a period of time

Bring your cat to a veterinarian as soon as you notice symptoms developing. The veterinarian will want to perform a complete physical examination of the cat to locate warbles under the skin. The vet will also have to differentiate between a Cuterebra infestation and other skin abscesses or foreign bodies. A CT scan is often requested to see the larvae in the body and to also map out its migration path. If the larvae traveled through the brain, there will be a mottled appearance in the images. This is especially dangerous as it can indicate brain damage. 

The warbles may be cream, grey, or dark in color, with the dark stage being accompanied by multiple spines on the back. An immunoabsorbent application may be administered, which can identify specific parasites in the body. Bacterial infections often develop secondary to Cuterebra infestations and should be identified for proper treatment. In some cases, the warble may have already exited the body, leaving behind an open wound prone to severe infection. 

If the larvae is removed while it is still small and before any other infection has developed, treatment is very effective. Certain locations of infestation can not be treated, such as the brain or spinal cord. 

Surgical Extraction 

If the warble has been identified under the skin, removal should be attempted. If a more developed larva is present, which are more commonly diagnosed, the breathing hole should be probed and expanded using mosquito forceps. This agitation may cause the larvae to sink further back into the pore. The breathing hole may be covered with petroleum jelly for up to 15 minutes to ease the extraction process. The bulge is never squeezed, as this can cause the warble to break into multiple pieces. This is dangerous, as it can cause the body's immune system to react and can lead to infection. These infections rarely may develop into anaphylaxis (a hypersensitive allergic reaction). The warble should be removed in one piece of possible. If it is too small to probe for, the warble and the surrounding tissue should be dissected. The wound should then be flushed with sterile saline. General anesthesia is required for both procedures.

Antibiotics 

Generally, antibiotics will be prescribed to the cat if a bacterial infection is present, or to ward off one from forming in the open wound. Antibiotic prescriptions usually last from one to four weeks.

If the warble has already exited the body, the wound should be thoroughly cleaned and an antibiotic prescription should be administered.

Once the cat is at home, do all that you can to ensure that the wound stays clean. Monitor the area for infection on a daily basis and bring the cat back to the vet if one begins to develop. Cuterebra removal carries a long healing process. If you notice an abscess form in the wound area, an infection has occurred or pieces of the larvae still remain under the skin. 

In most cases, the warble can be removed and the wound will heal. Serious complications may arise if multiple warbles have infested the cat, or their location is near nerves or organs in the body. If the traveling larvae have caused brain damage, there is a possibility that your cat may be left with behavioral abnormalities. Keeping your cat indoors can greatly reduce the chance of exposure to Cuterebra eggs. Applying a regular topical insecticide may prevent the larvae from surviving in the cat.