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Avian Medicine: General Avian Medicine:
Diseases of Songbirds: A “Cheat” Sheet

Date: July 17, 2012

Key words: Passerine, poxvirus, paramyxovirus, coccidiosis, tuberculosis, pseudotuberculosis

Introduction

Approach to the passerine relies on the same concepts of “One Medicine” used as in all animals (Fig 1). Nevertheless many of the infectious agents diagnosed in songbirds are relatively unique to this taxonomic group, or at least much more prevalent when compared to parrots or birds of prey.

sinusitis canary Echols

Figure 1. A differential diagnosis list using an “all one medicine” approach can only take one so far. Some causes of disease, such as sinusitis in this canary, can be relatively unique to order Passeriformes. Image by Dr. M. Scott Echols. Click image to enlarge.

Below you will find a collection of differential diagnoses for common clinical problems observed in the passerine. These abbreviated lists should in no way replace professional judgment when evaluating your patient. This “cheat sheet” is merely designed as an aide or reminder system and should never be used for diagnostic decision-making.

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Fluffed and ruffled

Rule-outs for the fluffed and ruffled songbird include:

  • Atoxoplasmosis (juvenile)
  • Chlamydiosis *
  • Egg binding
  • Poxvirus, septicemic form
  • Trauma
  • Yersinia pseudotuberculosis
  • * When compared to psittacines, passerines are less susceptible to Chlamydiosis. Signs of chlamydial infection in songbirds are often non-specific and mortality rates are low.


Atoxoplasma sp., formerly called Lankestrella, is an Isospora type coccidian parasite with a prolonged life cycle. Life stages involve the intestinal mucosa, mononuclear cells, and macrophages. Atoxoplasma has been described in a wide variety of passerines, but it is one of the most important infections of young canaries (Serinus spp.) between 2-9 months of age. Atoxoplasma also affects European finches such as the goldfinch, siskin, greenfinch, and bullfinch. Among zoo collections, this organism has been a documented problem in Bali mynah (Leucopsar rothschildi) fledglings.

The primary mode of transmission of Atoxoplasma is the fecal-oral route. Sporozoites invade intestinal epithelial cells, mononuclear cells, and then disseminate throughout the body. Infected adult birds can intermittently shed large numbers of oocysts for long periods of time. Clinical signs frequently include a fluffed and ruffled appearance and diarrhea. Neurologic deficits may be observed in up to 20% of affected birds, and up to 80% ultimately die.

Antemortem diagnosis of atoxoplasmosis is difficult. Oocysts are shed intermittently and the organism may be missed on fecal exam, even when samples are collected over several days. Other diagnostic tests can include buffy coat smears as well as liver biopsy or splenic aspirate. Definitive diagnosis often relies on identifying the parasite on impression smears of the intestinal tract. Atoxoplasmosis is also called “thick liver disease” and common gross necropsy findings include hepatomegaly and splenomegaly with pinpoint, necrotic foci. The pancreas may be edematous and the intestinal tract is often fluid filled.

Treatment of atoxoplasmosis is also challenging since the organism is resistant to sulfa drugs. Medications that have been tried with variable degrees of success (or failure) include sulfachlorpyridazine (Vetisulid, Boehringer-Ingelheim), toltrazuril (Baycox, Bayer), and diclazuril (Clinicox, Huevepharma). Management relies upon routine, scrupulous sanitation.

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Diseases of the chick

Important diseases of juvenile songbirds include:

Avian polyoma virus (APV) can cause sudden death in 2-3 day old chicks, particularly Gouldian finches (Chloebia gouldiae). In older chicks, APV can cause poor feather quality and an abnormal, tubular beak. Gross necropsy lesions can include a pale liver, splenomegaly, and hemorrhage.

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Disease of the gastrointestinal tract

Important causes of ingluvitis in the songbird include:

  • Candidiasis
  • Salmonella typhimurium var Copenhagen has been associated with granulomatous ingluvitis in European finches


Box 1. Causes of diarrhea in passerines

Category
Etiologic agent
Signalment
Comments
ParasiteAtoxoplasma sp.Canaries, European finches, Bali mynah
Cochlosoma sp.Bengalese (or Society) finchesMaldigestion diarrhea
Isospora canariaCanaries of all agesDiarrhea
BacteriaCampylobacter fetus var jejuniTropical finches (Estrildidae)“popcorn” feces
Enterobacteriaceae (E. coli)Canaries, finchesHemorrhagic enteritis in nestlings
Mycobacterium aviumRed hooded siskins
Pseudomonas sp.
Yersinia pseudotuberculosis
FungiAvian gastric yeast (Macrorhabdus ornithogaster)Diarrhea, depression, weight loss in the face of a voracious appetite

Pseudotuberculosis or yersiniosis is caused by Yersinia pseudotuberculosis. Pseudotuberculosis causes non-specific signs of illness and peracute mortality in finches and canaries and is most commonly observed during the winter months. Necropsy findings can include enteritis, liver and spleen absceses, catarrhal pneumonia, and typhlitis. Impression smears of affected organs reveales many rod-shaped bacteria. Research suggests that the best empirical treatment is enrofloxacin (Haesebrouck 1995), however collect samples for culture/sensitivity testing. The incidence of pseudotuberculosis is minimized by stressing sanitation and rodent control.

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Ophthalmic disease


Box 2. Ophthalmic diseases of passerines

Category
Etiologic agent
Signalment
Comments
VirusParamyxovirus type 1Weaver finchesDiarrhea
Poxvirus, septicemic formCanariesConjunctivitis, blepharitis
BacteriaStaphylococcus spp., Streptococcus spp.Conjunctivitis
ParasiteToxoplasma gondiiIridocyclitis
Panophthalmia
OtherCataractNorwich and Yorkshire canaries

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Respiratory disease


Box 3. Some important causes of respiratory disease in passerines

Category
Etiologic agent
Signalment
Comments
VirusPoxvirus, wet formCanary, finch, house sparrowDyspnea
Poxvirus, septicemic form
ParasiteSternostoma tracheacolum (tracheal mite)Canary, Australian finches
Toxoplasma gondiiPrevalent in Australia
BacteriaEnterococcus faecalisTracheitis, pneumonia, air sacculitis
Mycobacterium aviumRed hooded siskin
Mycoplasma spp.Canary, finches
Pseudomonas spp.
Streptococcus, StaphylococcusSinusitis
Yersinia pseudotuberculosis
FungiAspergillus spp.Mynah bird
Metabolic diseaseIron storage diseaseMynah bird

Among passeriforms, canaries and house sparrows (Passer domesticus) are most susceptible to poxvirus. All three forms of pox may be seen in passerines:

  • Dry or cutaneous
  • Wet or diptheritic
  • Septicemic

Canary pox can be devastating, causing mortality in up to 100% of affected birds. The clinical picture can range from non-specific signs of illness, such as lethargy and a fluffed and ruffled appearance, to dyspnea or conjunctivitis, blepharitis, and epiphora.

Early necropsy findings can include cloudy air sacs, pneumonia, necrotizing bronchitis. Later stages exhibit proliferative skin lesions and intracytoplasmic inclusions or Bollinger bodies are found on impression smears.

There is no treatment for poxvirus, and aggressive supportive care is required. Survivors of the septicemic form of disease can develop lung tumors. A vaccine for canary pox is available.

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Neurologic disease

Potential causes of neurologic deficits in passerine birds include:

  • Atoxoplasmosis
  • Listeriosis (torticollis, tremors, stupor, paresis, and paralysis); canaries particularly susceptible)
  • Paramyxovirus III (torticollis)
  • Toxoplasmosis
  • Toxic exposure
  • Trauma

The most common serotype of paramyxovirus (PMV) observed in passerines is PMV-3. Paramyxovirus type 3 has been isolated from canaries, finches, and weaver finches (family Estrildidae). Clinical signs can include anorexia, weight loss, diarrhea, neurologic signs like torticollis, dyspnea, and conjunctivitis. Gross necropsy reveals only mild, non-specific lesions. Diagnosis relies upon serology or viral isolation.

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Dermatologic disease

Causes of dermatologic disease in the passerine bird include:

  • Bacterial dermatitis (Staphylococcus spp., Streptococcus spp.)
  • Feather cysts (Norwich, Crested and Crest-bred canaries)
  • Fiber constriction of extremities
  • Fungal dermatitis
  • Knemidokoptes mites
  • Papillomavirus (bullfinches, chaffinches)
  • Polyoma virus (poor feather quality, abnormal tubular beak)
  • Straw feathers (canaries, zebra finches)

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Peracute death

Causes of sudden death can include:

  • Polyoma virus (adult finches after transport and other stressors OR 2-3 day old chicks, especially Gouldian finch )
  • Poxvirus (canaries, house sparrows)
  • Toxic exposure
  • Trauma
  • Yersinia pseudotuberculosis (finch, canary)

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Conclusion

Forming a differential diagnosis list for the passerine bird follows the same principles as in any other species, however some diseases are relatively unique to this taxonomic group. Also, keep in mind that several conditions are best identified at necropsy by impression smear, so be sure to routinely perform this procedure on major organ systems at every songbird necropsy.


References and further reading

Dorrestein GM. Passerines. In: Altman R, Clubb SL, Dorrestein GM, Quesenberry K (eds). Avian Medicine and Surgery. Philadelphia, PA: WB Saunders; 1997. Pp. 867-885.

Haesebrouck F. Effect of antimicrobial on the course of an experimental Yersinia pseudotuberculosis infection in canaries. Avian Pathol 24(2):273-383, 1995.

Manarolla G, Liandris E, Pisoni G, et al. Mycobacterium genavense and avian polyomavirus co-infection in a European goldfinch (Carduelis carduelis). Avian Pathol 36(5):423-426, 2007.

Sandmeier P, Coutteel P. Management of canaries, finches and mynahs. In: Harrison GJ, Lightfoot TL (eds). Clinical Avian Medicine. Palm Beach, FL, Spix Publishing, 2006. Pp. 879-913.

Shivaprasad HL, Kim T, Tripathy D, et al. Unusual pathology of canary poxvirus infection associated with high mortality in young and adult breeder canaries (Serinus canaria). Avian Pathol 38(4):311-316, 2009.


Written by Christal Pollock, DVM, Dipl. ABVP-Avian; Lafeber Company veterinary consultant.

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