Cardiopulmonary filariosis, now more briefly referred to as " Filaria ", is a disease that can affect cats and, in particular, dogs.
If it is not treated in time, the disease causes respiratory difficulties for the animal and eventually leads to death.
Causes
Filaria is caused by a parasite that completes its life cycle both inside an intermediate host (insect) and in a definitive host (the animal). This is because, the parasite - represented by the Dirofilaria immitis (class NEMATODI; order SPIRURIDA; suborder FILARIATA; family ONCHOCERCIDAE) - needs several phases to complete its biological cycle.
Vital Cycle of Filaria
The intermediate host - represented by the mosquitoes of the CULICIDAE family, genus Culex, Aedes and Anopheles - is a hematophagous insect (it feeds on blood). This mosquito, by pricking an infected animal (definitive host), ingests the micro-filarias ("L1" first stage larvae) with the blood.
These larvae, within the biological vector (mosquito), mature, after about seven days, in second-stage L2 larvae, and then develop, after another 6-7 days, into infecting L3 larvae.
Therefore, since the mosquito takes on the L1 microfilariae at the moment in which they become infectious L3 larvae (that is, they reach such maturity that they can then become adult and cause disease), about 12-14 days pass (given that the average life of one mosquito is about 15 days, each insect can only allow the development of a few microfilariae).
At this point, the infecting L3 larvae migrate into the buccal apparatus of the mosquito, which, by pricking a new host to feed on its blood, transmits the parasite.
The larvae, through the subcutis of the animal, migrate into the capillaries to become, after about 6-12 days, in L4 larvae. These, for some time, migrate inside the definitive host where they change, between the 50th and 70th day, to the adult stage L5, to then settle within the 120th day, in the heart and in the pulmonary arteries of our friend on all fours.
At 6 months after penetration of the L3 larvae of Dirofilaria immitis into the animal, the parasites become sexually mature and begin to produce microfilariae. After fertilization, the viviparous female (does not deposit eggs but gives birth directly to the offspring) releases the L1 micro-filarias in the circulation, which, especially at night, concentrate in the peripheral circulation (cutaneous vessels).
Mosquitoes, which start appearing at dusk, pricking the animal to feed on its blood, take microfilariae (L1) and start the cycle again.
In depth:
- Filaria in the dog
- Filaria in the cat
