A nationwide shortage of medication used to kill heartworms in dogs is "not catastrophic," say animal health professionals.
Duluth-based Merial, distributor of Immiticide, the only FDA-approved drug available to treat adult heartworms in dogs, sent letters earlier this month to veterinarians informing them of the depletion of inventory. The news was not unexpected; the company warned of production problems as far back as December 2009.
Merial spokesman Steve Dickinson said "technical issues" have halted the production of Immiticide by a third-party supplier. The company is "trying as hard as [it] can" to resume production or find an alternative supplier, he said.
Dickinson said one of the problems is that the active ingredient in Immiticide, melarsomine, is difficult to manufacture. Melarsomine, a derivative of arsenic, is effective at killing adult heartworms -- a parasitic roundworm transmitted by mosquitoes -- that infest animal arteries and can cause death.
Currently, Merial has no Immiticide to sell to veterinarians, said Dickinson. He did not know when production would resume, saying only that the problem could last several weeks or months.
Those in the animal health care field say that while the lack of Immiticide is a problem, it's no cause for panic.
Scott Zimmerman, a manager at Dearborn Animal Hospital in Decatur, said pets on routine heartworm preventative medication are at a very low risk of contracting heartworm disease.
But, dogs with adult heartworms can't "currently be treated with the best medicine," said Zimmerman.
The lack of Immiticide "is not a death sentence," said Becky Cross, founder of Atlanta Lab Rescue.
Cross said roughly half of the 350 animals her group find homes for each year must be treated for heartworms, which can cost upwards of $800.
"A lot of shelters that test for heartworms will just put animals to sleep," said Cross, who estimated more than half of the $120,000 Atlanta Lab Rescue spent on vet bills in 2010 was for heartworm treatments. "Lots of rescue groups won’t take heartworm-positive dogs"
Atlanta Lab Rescue will begin using a cheaper but less effective "slow kill" method to treat the infected animals it has up for adoption, Cross said.
The slow kill method, which only kills worm larvae, involves giving a dog monthly heartworm preventative medication -- which costs about $15 a month -- and waiting a year or more for the adult heartworms to die.
Dr. Duffy Jones, a veterinarian and owner of Peachtree Hills Animal Hospital, who works with Atlanta Lab Rescue, said the slow kill method is "not ideal" for two reasons -- it takes a year or more for the adult heartworms to die, which can lead to additional scarring of the dog's heart and lungs; and the animal cannot exercise during that time.
"The Immiticide being gone is problematic but not catastrophic,” said Jones, who stressed the need for routine preventative medication.
Dr. Susan B. Krebsbach, a veterinarian with the Humane Society Veterinary Medical Association, said the extended treatment schedule is likely to slow the adoption rate of shelter dogs.
"Dogs that test positive are going to be positive for a lot longer," she said.
Krebsbach said Merial's production problems have made vets more aware of less expensive drugs, such as doxycyline, an antibiotic that has proven to reduce the viability of heartworm larvae, which should reduce transmission rates. The antibiotic, combined with a heartworm preventative, also shortens the lifespan of the adult heartworms and lessens problems associated with worm death, she said.
Merial, the animal health division of Sanofi, employs 5,600 globally. About 600 work at the company's Duluth headquarters.
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