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The parasite cycle
C.P.F. is a disease that has clinical importance especially in dogs.
THE ETIOLOGICAL AGENT D.immitis (D.I) is transmitted by a mosquito carrier
and it completes part of its cycle inside the mosquito, before passing
onto a final host.
The adult parasite (macrofilaria) lives in the right-hand side of the
heart, in the pulmonary arteries, in the Vena cava caudal. In the larval
form (microfilariae) it lives in the peripheral blood. When a mosquito
bites an C.F.P. infected dog, it ingests larvae. After about 14 days,
the same mosquito biting another dog can transmit the disease. For a vet,
the disease is diagnosable after 6/8 months.
Once the adult parasites have reached the heart, they produce microfiliariae,
that live in the peripheral blood, allowing the start of a new circle.
I do not think it is necessary to give further reasons regarding the
intracardiac parasite cycle.
Therefore, there is no point in explaining the l3-l4-l5 phases, in recalling
the phases of the mosquito cycle and the reproduction method ... In quoting
the life cycle ... The length of the parasite's life, as the above is
fully documentated in the references.
Therefore, being a practical vet, i would like to express my experience
only with evidences.
Environmental conditions
The disease is spread worldwide: Europe, the United States, the Great
Canadian Lakes, China, Japan, the Pacific Islands and the coasts of Australia
(references).
In Italy, the disease is mostly spread in the Po Valley. Water is the
main element for the larval growth of the (mosquito) carrier. The environment
(rivers, lakes, ponds and ditches) together with the temperature, conditions
the life of the mosquito and therefore the propagation of the disease.
The factors that influence the continuous spreading of the disease in
spring, summer and autumn are:
- The dog's environmental conditions (final host);
- dogs that carry asymptomatic filariasis;
- the mosquito's environmental conditions;
- temperature.
- transporting animals when travelling/holidays.
C.P.F. is a disease that i also diagnosed in cats using the heska test.
Clinical aspects.
I agree, as you can read the references, that the incubation period of
the disease is around 6/8 months. C.P.F. is rarely diagnosable before
dogs are 8 months old.
The disease is not transmittable (mother-puppy) during pregnancy, as the
disease is only transmitted by a mosquito carrier.
In the references you can see the transmission of only mcrofilariae (in
pregnancy), which can never grow into adult parasites.
Dogs infected by C.P.F. can show clinical symptoms in relation to age.
For the vet and client, it is necessary to establish some parameters:
1) the dog's age and when the last time specific blood tests for the search
of parasites had been carried out;
2) a substantial level of microfilariae is not directly proportional to
the seriousness of the disease;
3) the lack of microfilariae in the peripheral blood is not sufficient
to state that the dog is not afflicted with filariosi;
4) the echocardiography assessment helps to validate the real quantity
of intracardiac parasites;
5) the ECG exam is used to show the atrial and right ventricular hypertrophy;
6) the thorax x-ray helps to identify changes in the cardiac profile and
the bronchio- pulmonary vasal texture etc;
7) the blood-cell count test often shows eosinophilia and an increase
in platelets.
Dogs infected with C.P.F. have clinical symptoms in connection with various
factors:
A) how long has D.I. lived in the animal?
B) the amount of parasites;
C) the age of animal;
D) general health of the animal.
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