Worms (hookworms, roundworms and tapeworms) commonly infect dogs and cats and also pose a threat to humans.
How do dogs and cats pick up worms?
Worms or internal parasites can be picked up by:
- licking the ground or drinking contaminated water
- ingesting infected fleas which can transmit tapeworms
- through the placenta before birth from the mother to the puppies
- through the milk of the mother to the unweaned kittens and puppies
- from scavenging or hunting
- eating raw offal, which could be infected with tapeworm cysts.
How do I know that my pet has worms?
Pets rarely pass worms, and even if they do, you will rarely see them. The symptoms of a worm infestation can be one of the following:
- Bloody stools
- Loss of appetite
- Anaemia (pale gums and eye membranes)
- Weight loss
- Poor growth
- Pot-bellied appearance
- Loss of vision in one or both eyes
Tapeworm segments are released with the droppings (faeces) and are clearly visible in the faeces or around the anus of the animal. These segments look like rice grains.
Is a worm infestation dangerous?
A heavy worm infestation can cause enteritis with a resultant diarrhoea which can even contain blood and mucous. Some worms suck blood, which causes blood loss in the animal leading to weakness and even death. Heavy worm burdens can block the intestines and lead to the death of the animal. Another danger of worms lies in the transmission from dog or cat to humans. Many worms can cause serious health problems in humans as well.
How can I protect myself?
- Always wash your hands after working or playing with your pets.
- Never allow dogs or cats to lick your face.
- Fence off vegetable gardens to prevent dogs or cats defecating in these areas.
- Wash all vegetables thoroughly before eating
- Never share cooking utensils with pets.
- Never feed raw offal to your pets – make sure it is well cooked
- Deworm your pets and family regularly.
How do I treat my dog or cat for worms?
Every adult dog or cat should be given a dewormer every 3-4 months and puppies and kittens every three months. This should be done in co-operation with your local Community Veterinary Clinic or veterinarian.
It is also very important to deworm family members at least twice a year – speak to your doctor or pharmacist.
Note: Do not feed your pet raw offal. It could be infected with tapeworm cysts.
Spirocerca lupi - The "worm in the throat"
A worm called Spirocerca lupi is becoming more common in South Africa’s summer rainfall areas, leading to an almost endemic situation. This worm lives in the dog’s oesophagus where it forms a nodule. Many worms can live inside a nodule and numerous nodules can form.
The female lays eggs and these are passed in the stool of the dog (host). These eggs have to be eaten by a dung beetle (intermediate host) for the lifecycle to continue. The small dung beetles (scarab beetles) living in the stool are part of the lifecycle, not the dung rollers we are more familiar with. he beetle can be eaten by the dog or another small mammal. The egg hatches and matures to a larval stage three in the beetle and stays in that phase even if eaten by other small mammals, lizards or birds. Further maturation will only occur if the host (beetle or transport host) is eaten by a dog.
The third stage larvae hatch and burrow into the stomach wall where they migrate along the arteries back towards the chest portion of the aorta, the main blood vessel in the body. This takes about two weeks. Once in the aortic wall, the worms mature and stay there for about three month. Extensive damage is caused to the aorta during this period and aneurysms develop. These may rupture and cause acute death. Once the worms are mature, they migrate directly across the body tissues to the oesophagus which lies adjacent in the chest.
At this stage these worms are about 4-5 cm long and can cause considerable damage, resulting in rupture of large blood vessels, inflammation of the lining structures of the lungs and infection.
The worms then establish themselves in the oesophagus where they live, mate and lay eggs. Dogs react differently to these nodules: some dogs, especially fox terriers, show signs of sever irritation with even small nodules (gagging, swallowing, retching) whereas other dogs may show no symptoms until the nodules are large.
Other symptoms associated with the migration can be fevers, joint pain, coughing, and difficulty breathing. With time, and due to the chronic irritation caused by the worm in the tissue, these nodules can become cancerous. This is a serious condition which may or may not respond to surgery depending on the extent of the cancer.
Diagnosis is best made by doing an oesophageal endoscopy (putting a camera into the oesophagus) and observing for a nodule. Chest X-rays can also help, but may miss some nodules. Not all nodules grow into the oesophagus and a CT scan might also be used to check for these.
The worm sometimes gets lost and can make nodules in just about any organ. This is called aberrant migration. If one of your dogs is diagnosed with this worm it is advisable to have all your other dogs checked. Preventative therapy is not yet proven beyond a doubt but evidence shows that you will decrease your chances of re-infection by 80% if you deworm your dogs monthly with a dewormer containing milbemycin oxime (Milbemax®), or use a cattle dewormer doramectin. These anti-parasiticide agents are the only proven drugs to cure and decrease the infection with Spirocera lupi. Spot-on preparations containing these drugs do exist, but there is no evidence that they are effective in treating spirocercosis. Worms that are exposed to these drugs also lay fewer eggs, even before they die, thus decreasing environmental contamination.
Deworming your dog monthly is the preferred method of controlling all other worms (round and tapeworm) as their lifecycles are about 21 days long and monthly deworming prevents them from maturing and laying eggs, contaminating your environment.
This disease has not been documented to affect humans, and only rarely cats. So take the bull by the horns with this devastating disease and get your dogs checked by your veterinarian and start a monthly preventative program.
Compiled by: Dr Liesel van der Merwe, Valley Farm Animal Hospital, Pretoria