Marmoset Wasting Disease:

A Cause Found At Last?

 

 

 

 

By:  Margaret Wissman, DVM, DABVP

 Marmoset wasting disease is a devastating problem found among marmosets and perhaps tamarinds, as well. Symptoms may include weight loss in spite of a voracious appetite, emaciation, muscular weakness, disorders of coordination progressing to paralysis of the hindquarters, chronic non-responsive diarrhea, lethargy, rough hair coat, and hair loss on the tail. The disease may spread through a colony causing devastating losses. Up to now, many causes have been suspected, including a virus, bacteria, autoimmune disease, disease similar to Crohnís disease in humans, nutritional deficiencies or excesses, or parasites.

Some work has been performed at CIBA-GEIGY because of losses that decimated their marmoset collection in 1983 and again in 1986. Tests showed large numbers of a type of parasite worm called Trichospirura leptostoma, that lives in the pancreas of marmosets. A study performed in 1967 showed that wild-living marmosets often had between 1 and 31 worms in the pancreatic ducts, although less than ten were usually present, and usually no clinical signs were seen, or there may have been a non-specific atrophy of the exocrine pancreas. However, in the monkeys autopsied at Ciba-Geigy, up to 300 worms and larvae were found in the pancreatic ducts.

They then performed studies to show that two types of cockroaches carry the larvae of the pancreatic worms and can transmit them to marmosets when they catch and eat roaches. These cockroaches are called intermediate hosts. Their research showed that the entire life-cycle of T. leptostoma lasts between 14 and 15 weeks, including 5-6 weeks in the cockroach. The intermediate host in nature is not known. After experimental infection in marmosets, the prepatent period (the period between the time of introduction of parasitic organisms into the body and their appearance in the tissues) is estimated to be 8-9 weeks. The worms can reproduce for about 12 years, and after that time no further eggs are found in the feces, although worms containing embryonated eggs persist in the pancreas.

Diagnosis of pancreatic duct worms in a live marmoset can be difficult. Worm eggs containing fully developed larvae are only sporadically detected in the feces in clinically ill marmosets. Eggs are only excreted very infrequently and at irregular intervals. It may be necessary to perform three separate tests on the feces to try and identify these parasites: fecal flotation, fecal smear and tests for larvae in the feces, and even then, these tests may need to be performed repeatedly to identify the worm eggs.

Treatment for ill marmosets may include supplementation with pancreatic enzymes, vitamin supplementation, nutritional supplementation, support care (fluids, heat) and treatment for any secondary infections. At Ciba-Geigy, all infested animals were sacrificed. For pet marmosets, treatment to kill T. leptostoma may be attempted. Recent research indicated that fenbendazole given orally for 14 days may be effective. The difficulty is in finding a dewormer that penetrates well into pancreatic tissue. More research needs to be performed in this area. I am not including a specific dose, as treatment should only be performed by a qualified veterinarian familiar with anthelmintics.

Damage to the pancreas may lead to permanent pancreatic dysfunction, so early diagnosis and treatment is necessary to prevent future problems. I have recently diagnosed my first common marmoset with T. leptostoma. She was a 2 year old female that had 6 month old twin babies that she and her mate successfully raised. She died en route to my hospital. She has been acting weak for several days, then on a Saturday, she became paralyzed in her hind legs. On necropsy (autopsy), she was not emaciated. It is important to any vet performing necropsies on marmosets and tamarinds to make sure that they submit pancreas for histopathologic evaluation. Often, the pancreas will be atrophied (shrunken) and may not be even visible. So, the vet must send in the duodenal loop that normally contains pancreas, even if it is not visualized.

Although researches are still debating the cause of Wasting Disease, I firmly believe that the cause is the pancreatic duct worm, T. leptostoma. Treatment may be difficult, and as more information is available, I will update our readers. Control of cockroaches and other insects is extremely important for owners of Callitrichids (marmosets and tamarinds). I do have scientific papers that I have read that do indicate that this parasite is also found in tamarinds.

Marmoset wasting has been a terrible problem in many colonies and in some pet Callitrichids. Because of the protracted course of the disease, it is heartbreaking for the owners and horrible for the effected animals. It has been a very frustrating problem, and now that a true suspected cause has been found, it will be possible to develop a protocol to effectively eradicate the worms from the pancreas. I hope. It is very important for owners of animals with signs of wasting to have multiple fecal examinations performed, and if any animals die, they should be thoroughly necropsies and tissues submitted for microscopic examination. Make sure the vet knows to send in a sample of pancreas for examination, as well. I think, in the past, many vets missed sending in pancreas because it was atrophied and not visible, and therefore the diagnosis were missed. As owners of Callitrichids, we should be responsible about having diagnostics performed on sick animals, and ALL marmosets and tamarinds that die should be necropsies and have appropriate diagnostics performed to determine WHY they died, to advance knowledge of medicine of these little guys. If we donít do it, we wonít be able to help the survival of these small, beautiful monkeys in the future.

Dr. Wissman owns and operates, along with her husband, Bill Parsons, Small World Zoological Gardens and Sanctuary in Florida, for the captive conservation of Callitrichids. She is a Board Certified Avian Specialist who writes frequently for the SSA, Inc. She is very active in promoting proper husbandry and medical care for primates. She is a member of the Association of Primate Veterinarians.

 

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