Question

Question: You are assessing an animal that was brought across the state. The animal has a cough, intolerance to exercise, difficult breathing (dyspnea), and the mucosa of the cat looks anoxic (lack of oxygen). The heart rate is 150, with the normal ranging from 120-140 along with rapid breathing. An x ray was conducted and the heart was enlarged, and also had an enlarged pulmonary artery. A blood sample was also obtained, however the only thing that was elevated was the eosinophils and the basophils. You are suspecting a possible case of heart worm (HW) disease (dirofilaria imitis).

a. If this animal is affected by a parasite, what are the physiological implications? (Be sure to mention four things from the physiological standpoint that can be affected).

b. What is a good method of diagnosis in cats to determine if heart worm disease is present?

c. What is a preventive measurement for heart worm disease, mention the drug and the frequency of administration.

Answer 1

Question A

Answer

Parasites that infest cattle, sheep and goats include internal parasites, such as worms, flukes and protozoa, and external parasites, such as flies, ticks, lice and mites.

Of the endemic diseases that affect livestock in Australia, parasitic diseases have the largest financial impact on farm productivity.

A recent MLA project that assessed the financial impact of endemic diseases on farm productivity found that five of the eight highest cost diseases of cattle and sheep are caused by parasites (worms, flystrike and lice in sheep and cattle tick and buffalo fly in cattle).

Important considerations in the management of parasites in livestock are:

• Identification
• Control
• Chemical resistance and residues

Impact on animal health and welfare

Parasites can have a negative impact on the health and welfare of animals:

• Some parasites cause blood loss which, if substantial, can lead to anaemia and death.
• Other parasites cause diarrhoea which, if severe, can lead to death.
• Infestation with parasites can reduce the appetite of animals, resulting in debilitated animals that are more susceptible to other diseases.
• Parasites can also act as vectors, transferring diseases from one animal to another.
• External parasites like flies cause open sores on the skin of livestock.
• Flies can also annoy animals, causing them to reduce grazing behaviour or, in severe fly waves, become very agitated (fly worry).

Impact on livestock productivity

These harmful effects can have a negative effect on the productivity of livestock by:

• Reducing growth rates.
• Reducing reproductive rates.
• Causing condemnation of carcase parts at slaughter.
• Reducing milk production.
• Reducing fleece weight, fibre diameter and staple strength.
• Damaging hides and fleeces.

Parasites of livestock can also be zoonoses, meaning humans can become infected as well eg hydatid tapeworm found in sheep and dogs.

Some parasites of cattle, sheep and goats are not found in Australia, for example screwworm fly and some types of mites. It is important to keep these parasites out of Australia, industry biosecurity helps ensure this.

Parasite problems and floods

Following flood events (or significant amounts of rain), the populations of biting insects (buffalo fly, midges, mosquitoes and stable fly) and ticks can increase dramatically.

Producers need to be aware of this and implement proper control measures to prevent animal welfare issues and losses in productivity.

Question B

Answer

Heartworm disease typically affects dogs, but occasionally occurs in cats. The disease is caused by a parasite called Dirofilaria immitis, better known as heartworm. The parasites are long, hair-like worms that prefer to live in the right side of the heart and the pulmonary artery, which is the large blood vessel that carries blood from the heart to the lungs. Cats become infected when they are bitten by an infected mosquito carrying infective heartworm larvae. When an infected mosquito bites a cat, the larvae pass from the mosquito into the cat.

Is heartworm disease the same in cats as it is in dogs?

Dogs are the normal host for heartworms. This means parasites are able to complete their life cycle in dogs, maturing into adult worms that live in the heart. These adult worms are able to mate and reproduce in dogs, producing immature worms called microfilaria that circulate in the bloodstream.

Question C

Answer

Heartworms (Dirofilaria immitis) are parasitic roundworms that can infect both dogs and cats. If your pets are not on pet prescription heartworm medicine, they may contract the parasite through the bite of an infected mosquito. Heartworm disease is preventable if you diligently use heartworm prevention prescribed by your veterinarian.

Dogs are “natural” hosts to heartworms, meaning that once they become infected, the juvenile heartworm parasites can complete their entire life cycle. As the heartworms mature, they work their way into your dog’s heart, lungs and associated blood vessels. Once there, they can grow to be up to a foot long. It is possible for one dog to be infected with hundreds of heartworms.

If not treated properly, heartworms in dogs will lead to serious health complications and death. This is why it is so important to keep your dog on continuous heartworm prevention.