Infectious disease in camelids

By: Seyedamin Razavi

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Infectious diseases play a prominent role in the production of camelids.Prevention, diagnosis, and treatment are vital to the management of theseanimals. It is appropriate to reiterate here that camelids are not ruminants.

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"Camel" is also used more broadly to describe any of the six camel-like mammalsin the family Camelidae: the two true camels and the four New World camelids:the llama, alpaca, guanaco, and vicuña of South America.

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Viral disease

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RabiesRabies is a viral encephalitic disease endemic in many areas of the world.Epidemiology: Rabies virus is primarily spread by bites from infected animals. Thevirus has been found in saliva and other body excretions, but it cannot penetratethe unbroken skin. Reservoir hosts vary with location. In Peru, the dog and fox areconsidered to be reservoir hosts. In tropical South America and Mexico, the vampirebat is a serious threat to livestock production. Because camelids are susceptible,they should be protected against infection by appropriate vaccination.Clinical Signs :Early signs of rabies in camelids include lameness, ataxia, andposterior paresis. Early signs are followed by either an aggressive syndrome (furiousrabies) or a paralytic syndrome (dumb rabies).Vocalization changes (alarm cries without cause) and other signs that have beenobserved during the course of the disease include bloat, pruritus, muscle tremors,aimless running. Paralytic rabies in camelids is characterized by anorexia,depression head droop, ptosis, tenesmus, salivation, circling, facial paralysis.

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Diagnosis: The rabies virus causes a nonsuppurative encephalitis with perivascularcuffing by mononuclear cells. Neuronal degeneration is seen. Camelids developNegri bodies in neurons of the hippocampus and other locations in the brain.Fluorescent antibody staining of neural tissue is usually the first screening testperformed in most laboratories.Prevention: killed rabies vaccines have been used and are appropriate forimmunization of camelids. Annual revaccination is recommended.

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HerpesvirusEpidemiology: Equine herpesvirus type 1 has been reported from a Bactrian cameland it should be assumed that dromedaries are also susceptible to the virus.Clinical Signs: Blindness, with nonresponsive dilated pupils, was the primarymanifestation in animals in the affected herd.Diagnosis: The lesions noted at necropsy included retinal detachment andhemorrhage, retinitis, choroiditis, and optic nerve degeneration.Treatment: Antiviral therapeutic agents have been used, steroids and othermedications were administered to llamas and alpaca, the retinal lesions wereunresponsive.Prevention: Each vaccine is prepared for a specific animal. Each animal respondscharacteristically Killed vaccines were given to exposed camelids.

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Contagious EcthymaEpidemiology: The natural reservoir host is probably the sheep. The virus may remain crusts from a lesion for longer than a year. Transmission may be by either direct contact or insect vectors. CE is a zoonosis that produces lesions on the fingers, limbs, or face of affected people.Clinical Signs: Young camels are also typically susceptible animals. The lesion may be chronic, characterized by thickening of an area of the differentiated from those of sarcoptic mange or ringworm.Diagnosis: The CE virus grows in tissue cultures but grows poorly on the chorioallantoic membrane of chick embryos. Microscopic lesions are diagnostic in early and acute cases.Treatment: No specific treatment is recommended.Prevention: Modified live virus (MLV) vaccines are routinely used in sheep and goats, but these vaccines are risky and may be unwise to use on camelids. Any sheep or goats kept with camelids should be vaccinated.

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Foot - and - Mouth DiseaseEtiology: FMD is caused by Aphthovirus sp. (Family Picornaviridae).Epidemiology: Many species of artiodactylid are susceptible to FMDV, butthey vary markedly as to whether or not clinical manifestations develop. The route of field transmission may be by respiratory aerosol, direct contact with infected animals, or exposure to contaminated feed and water.Clinical Signs: Experimentally infected camelids in Peru developed fever up to 40 ° C (104 ° F). This was the first sign noted in all affected animals. They became totally anorectic. Vesicle locations and progress of the lesions followed patterns seen in cattle and sheep.Diagnosis: Specific vesicular diseases cannot be differentiated by clinical signs nor at necropsy. Rinderpest must also be included in a differential diagnosis.Treatment: There is no treatment for FMD.

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Camel poxCamelpox is the most frequently seen infectious disease of both dromedaryand Bactrian camels, and has been produced experimentally in NWCs. Thedisease primarily affects younger animals.Etiology: The infective agent is Orthopoxvirus cameli (Family Poxviridae,Subfamily Chordovirinae).Epidemiology: Transmission is via viral exposure to abrasions or breaks inthe skin, aerosols, or mechanical transmission by biting insects or otherarthropods (mosquitoes, ticks).Clinical Signs: The incubation period is nine to thirteen days. In mild casespustules develop on the muzzle, nostrils, eyelids, oral mucosa, and nasalmucosa. The pathogenesis of the pox lesion starts as an erythematousmacule, progressing into a papule and then a vesicle. The vesicle changesinto a pustule with a depressed center and a raised erythematous border.When the pustules rupture they become encrusted.

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Diagnosis: Laboratory diagnosis may include inoculation of embryonated chicken eggs, cell cultures, and inoculation into rabbits. treatment : There is no specific treatment for camelpox.

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FUNGAL INFECTIONS

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Dermatophytosis (Ringworm)Etiology: Trichophyton verrucosumis the common cause of ringworm.Arthroconidia are seen lining the surface of hairs in potassium hydroxide (KOH)preparations of material scraped from lesions. T. mentagrophytes var.mentagrophytes has also been isolated from skin lesions in llamas. Species thathave been isolated from OWCs include Trichophyton verrucosum, T.mentagrophytes, T. schoenleinii, T. sarkisovii, T. dankaliense, Microsporumgypseum, and M. canis.Clinical Signs: Clinical cases may simply be alopecic areas with limited distributionon the head and neck or more generalized over the body and limbs. the lesions inthe llama were crusty, circular plaques around the face. the plaques varied from 2to 4 cm in diameter.Diagnosis: Direct microscopic examination of hair and crusts taken from theperiphery of a lesion is the most rapid method of diagnosis.

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Treatment: Lesions of ringworm are usually self - limiting in most species.Iodine (2% tincture) may be applied directly to a lesion daily for two weeks.A less caustic povidone - iodine preparation (diluted 1:4) may be equallyeffective. Thiabendazole has antifungal action and may be applied as a 2%to 4% ointment to lesions of ringworm at three - day intervals.

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CoccidioidomycosisCoccidioides immitis was first described as a protozoa, similar to coccidia, but it is actually a dimorphic fungus .Its life cycle is usually completed in the absence of animals.Epidemiology: NWC s appear to be highly susceptible to coccidioidomycosis,which is acquired by inhalation of arthrospores from a contaminated environment. Arthrospores are the infective stage; they convert to the tissue -invasive spherules seen in animal tissues. When the spherules rupture,endospores are released, spreading the infection. Coccidioidomycosis is an infectious disease, but it is not transmitted by direct contact from animalto animal.Clinical Signs: Clinical signs vary with the location of the lesion. Althoughdisseminated lesions were seen at necropsy in the heart, lungs, liver, and alllymph nodes, primary signs were neurologic. In other cases, respiratory signshave predominated, dyspnea and coughing. A dermal form is characterized bynodular lesions from 1 to 3 cm in diameter .Pruritus is not evident.

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Pathology: In less severe forms of coccidioidomycosis, granulomas may berestricted to the thoracic cavity and lymph nodes and within lung tissue.Treatment: 1 mg/kg amphotericin B, administered intravenously every forty – eighthours for six weeks. Several other antifungal imidazole drugs or combinations ofdrugs are used to treat coccidioidomycosis in humans and other animals.

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BACTERIAL DISEASES

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BotulismC. botulinum is distributed worldwide. The syndrome is believed to be similar to thatseen in most other mammals, consisting of a progressive paralysis of all skeletalmuscles. Initially, incoordination, muscle weakness, and recumbency are seen,leading finally to flaccid paralysis of all muscles, including respiratory muscles. Bodytemperature is not elevated. The pupils of the eyes become dilated. Salivation isdecreased, and mucous membranes become cyanotic.DIAGNOSIS: Because C. botulinum may be cultured from a normal digestive tract,isolation of the organism can be made only by the injection of filtrates of suspectedfeed materials or gut contents into mice or guinea pigs.TREATMENT: Once signs have developed, little can be done other than to supportrespiration.

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TetanusC. tetani occurs worldwide as a soil saprophyte, but it can also be found in thefeces of horses, humans, and cattle. Tetanus is more common in tropical regionsthan in cold climates. Tetanus develops when wounds have been contaminatedwith soil or feces containing C. tetani spores.CLINICAL SIGNS: Signs included prostration, muscle rigidity, dyspnea, tonicmuscular contractions, joint stiffness, erect ears, a locked jaw, and a fever of 41.5° C (107 ° F).TREATMENT: Tetanus antitoxin was administered at a dose of 225 units/kg bodyweight; half was given in an IV dose and half in an IM dose. Anaphylactic shock isa hazard of this therapy because tetanus antitoxin is a horse serum product.

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EnterotoxemiaC. perfringens is an anaerobic, spore - forming bacterium. Small numbers of theorganism may be found in the gastrointestinal tract of healthy individuals.Epidemiology : C. perfringens organisms (both spores and vegetative forms) areingested in feed or water. Type A enterotoxemia is the most serious disease ofneonate alpacas in Peru.Clinical Signs : Sudden death may be the only overt manifestation. Signs, and theirintensity, depend upon the quantity of toxin produced. Rectal temperaturesmay be subnormal, normal, or slightly elevated. Diarrhea is not a sign of type Aenterotoxemia but may be seen in mixed infections with Escherichia coli or othermicroorganisms.TREATMENT: Administration of broad - spectrum antibiotics may arrest the growth ofthe organism and production of toxins, but usually severe organ damage has alreadyoccurred. Supportive treatment with fluids is indicated, but the prognosis is grave.

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TuberculosisEpidemiology: Tuberculosis is a worldwide disease that usually develops slowlyLesions are commonly found in the respiratory and digestive systems, and excretions and secretions may be contaminated with the organism. Infection may be acquired by inhalation or ingestion.Clinical Signs: The signs of tuberculosis vary widely, depending on the organ system involved. Tuberculosis is a debilitating disease, so weight loss and emaciation aretypical. Diarrhea and dyspnea may accompany lesions in respective organ systemsTuberculosis is a highly chronic disease .Diagnosis: The ante mortem diagnosis of tuberculosis presents a challenge. Intradermal tuberculin testing is the classic diagnostic test, but modern diagnostic methods include lymphocyte stimulation tests, ELISA ,serologic testing.Treatment: Treatment is not allowed in the United States. Prevention: Tuberculosis vaccines are illegal in the United States.

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AnthraxAnthrax is an acute, septicemic disease of many species of mammals, including camelids. It is caused by Bacillus anthraces , a spore - forming, Gram - positiverod that is a constituent of the normal flora of many soil types worldwide.Clinical Signs: The incubation period ranges from one to fourteen days.fist sign of anthrax is fever, as high as 42 ° C (108 ° F), but this may be missed. The general signs of total anorexia, stomach stasis, colic, hematuria, and hemorrhagic diarrhea may be more evident. Sudden death may occur without premonitory signs being observed.Diagnosis: Anthrax may be confused with other diseases that cause sudden death or produce septicemia. B. anthraces is easily cultured from the tissues of the carcass. Ifanthrax is suspected, it is prudent to avoid a complete necropsy.

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Treatment: If a rapid diagnosis is made, B. anthraces is susceptible to many antibacterial agents, including penicillin and tetracyclines. Therapy should be continued for five or more days.Prevention: Live - spore bacterins are routinely used to protect camelids.It is inappropriate to administer antibiotics simultaneously with the bacterin, because this will inhibit or prevent development of antibodies.

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ListeriosisListeriosis (circling disease, listerellosis, silage disease) is caused by Listeriamonocytogenes , a Gram - positive nonspore - forming coccobacillus that has aworldwide distribution. The disease is infectious but not highly contagious,causing sporadic occurrence in a broad range of animal species, includingNWCs and OWCs. The herd morbidity is low, but the mortality rate of affectedindividuals is high.Clinical Signs: Camelids develop an encephalitic syndrome, similar to that seen incattle, with unilateral facial paralysis, circling, trembling of the head, running intoobjects, erect ears that may each be pointed in a different direction, salivation,depression, and a fever as high as 41.5 ° C (107 ° F)Death occurs two to fivedays after onset of the first signs of illness.Treatment and Prevention: Treatment of clinical cases has been unsuccessful todate. The disease appears to be rare in camelids; therefore,no vaccination program is recommended.

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Osteomyelitis of the MandibleEtiology and Epidemiology: Inflammatory swellings of the mandibles are seen in mammals throughout the world. Such swellings may be caused by dental anomalies or infections, tumors, trauma, or infection of the bone by osteolytic or proliferative bacteria. Both Actinomyces and Fusobacterium should be considered in a differential diagnosis in camelids.Clinical Signs: Firm swellings along the rami of the mandible are easily observed and palpated. Little or no pain may be associated with palpation. General signs of anorexia, fever, and depression are usually absent.Diagnosis: Surgical extirpation and microscopic examination of the lesions may aid in the diagnosis.Treatment and Prevention: Therapy is entirely dependent upon the etiologic agent and the nature of the lesion and may include surgery, administration of antimicrobials, and supportive therapy. No effective preventive measures have been developed.

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PasteurellosisPasteurella spp. and Mannheimia spp. are common causes of respiratory infection in numerous species of animals. The species of concern in camelids are Pasteurellamulticida in OWCs and Mannheimia haemolytica reported in NWCs.Epidemiology :These organisms may be normal inhabitants of the respiratory mucous membranes. Stress is a major predisposing factor. Transmission may occur from direct contact, inhalation, or ingestion.Clinical Signs: Infection is typically associated with the respiratory system, with septicemia a common sequel. The syndrome is characterized by fever, nasal discharge, lacrimation, dyspnea, diarrhea, congestion of mucous membranes, and lymph node swelling.Diagnosis: Pasteurella and Mannheimia may be cultured from the exudate from the respiratory tract and infected tissue. Management :Broad - spectrum antibiotics are indicated based on culture and sensitivity. Vaccines are used in ruminants, but have not been reported to be used in camelids.

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The end

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