I live in keysborough, vic and about 5 years I took my boy to my vet for the yearly heartworm injection (when it first came out) as my vet injected him - I asked why didnt he do a heartworm test first as thats what they use to do before you could start taking tablets if not already being treated... his answer ... was that he had not seen heartworm at his clinic for over 10 years now, and didnt bother to test for it... well that was $100 well spent... lol... have never used prevention since....
I remember doing some research on the mosquitoes that carry the larva once, the conditions have to be exact for them to evolve, its not just any mosquito just one type... (could be wrong here been a few years)...
Course of infection
Microfilaria (as seen at 400X magnification)Heartworms go through several life stages before they become adults infecting the heart of the host animal. The worms require the mosquito as an intermediate stage in order to complete their life cycle. Development in the mosquito is temperature dependent, requiring approximately two weeks of temperature at or above 27 °C (80 °F). Below a threshold temperature of 14 °C (57 °F), development cannot occur, and the cycle will be halted. As a result, transmission is limited to warm months, and duration of the transmission season varies geographically. The period between the initial infection when the dog is bitten by a mosquito and the maturation of the worms into adults living in the heart takes 6 to 7 months in dogs and is known as the "prepatent period".
After infection, the third stage larval heartworms (L3) deposited by the mosquito grow for a week or two and molt to the fourth larval stage (L4) under the skin at the site of the mosquito bite. Then they migrate to the muscles of the chest and abdomen and 45 to 60 days after infection, molt to the fifth stage (L5, immature adult). Between 75 and 120 days after infection these immature heartworms then enter the bloodstream and are carried through the heart to reside in the pulmonary artery. Over the next 3 to 4 months they increase greatly in size. The female adult worms are about 30 cm in length, and males are about 23 cm with a coiled tail. By approximately 6.5 to 7 months after infection, the adult worms have mated and the females begin giving birth to live young, called microfilariae.
The microfilariae circulate in the bloodstream for as long as two years, waiting for the next stage in their life cycle in the gut of a bloodsucking mosquito. When ingested by a mosquito, the microfilariae undergo a series of molts to the infective third larval stage and then migrate to the salivary glands of the mosquito, where they wait to infect another host. The incubation period required to reach the stage where the microfilariae become transmittable to another host can be as little as two weeks or as long as six weeks, depending on the warmth of the climate, and the larval life cycle ceases entirely if the ambient temperature drops below 14° Celsius (57° Fahrenheit).
There are currently 1 users browsing this thread. (0 members and 1 guests)