A common presenting complaint from parrot owners is that their pet has diarrhoea. In fact, this is one of the most common reasons for clients to bring their parrot to the vet (Hatt, 2018). Diarrhoea can be caused by several underlying conditions or diseases (Table 1); however, before attempting to diagnose and treat this clinical sign, it is important for veterinarians to determine if the parrot has true diarrhoea.
|Common differential diagnoses for parrots with true diarrhoea||Common differential diagnoses for parrots with polyuria|
|Change in diet||Excessive fruit intake|
|Chlamydiosis||Conversion to a pellet-based diet|
|Enteritis (bacterial, fungal or parasitic)||Stress|
|Macrorhabdus ornithogaster (also referred to as “megabacteria”)||Hypocalcaemia|
|Hepatic disease||Renal disease|
|Heavy metal toxicity (zinc and/or lead)||Diabetes mellitus|
|Proventricular dilatation disease (caused by avian bornavirus)||Systemic infections (viral, bacterial, fungal)|
|Heavy metal toxicity|
Because of [parrots’ gastrointestinal] physiology, it is crucial to determine if the diarrhoea reported by the client is true diarrhoea or if it is an increase in the urine component of the droppings, known as polyuria
Birds have one universal terminal opening for the digestive, urinary and reproductive systems, called the cloaca. The cloaca is separated by mucosal folds into three sections: the coprodeum, the urodeum and the proctodeum (King and McLelland, 1985). The coprodeum is the terminus of the large intestine, where faeces gathers for expulsion, and is separated from the urodeum by a thin mucosal membrane, which prevents faecal contamination of the urodeum (King and McLelland, 1984). The urodeum is where the ureters and reproductive ducts (oviduct in females, ductus deferens in males) terminate (Doneley, 2016a). The proctodeum is the final section that lies between the mucosal fold that separates the urodeum and proctodeum and the lips of the vent, which is the outer portion of the cloaca. When a parrot passes droppings, waste from the gastrointestinal system and urinary system are expelled together. This includes faeces, urates and urine (Figure 1). Because of this unique physiology, it is crucial to determine if the diarrhoea reported by the client is true diarrhoea (Figure 2) or if it is an increase in the urine component of the droppings, known as polyuria (Figure 3).
Polyuria can have several underlying causes (Table 1), so mistakenly treating polyuria as true diarrhoea can exacerbate the condition as the underlying cause may remain untreated. Once true diarrhoea has been determined, a full husbandry review and clinical history should be obtained. Any environmental or dietary changes should be of particular interest. A full physical examination should be performed to assess for any signs of underlying disease. Some of the most common causes of diarrhoea are discussed below; however, this discussion is by no means exhaustive, and any veterinary surgeon presented with a parrot with diarrhoea should consider this a clinical sign rather than the disease process itself.
Polyuria can have several underlying causes, so mistakenly treating polyuria as true diarrhoea can exacerbate the condition as the underlying cause may remain untreated
Diagnosis and treatment
Diet can be a common contributor to changes in faecal consistency. In some species, a liquid or soft faecal component is normal, especially for those with a high fruit and nectar content in their diet, like lories and lorikeets. Birds with a healthy and varied diet (for example, pellets, vegetables, fruits and berries) often have softer faeces due to the higher water content in these foods compared to seed. Seed-based diets should be discouraged, as they are high in fats and phosphorus and deficient in calcium, vitamin A and vitamin E (Doneley, 2016b).
Recommendations for diet are species-specific; however, as a rule of thumb, the more water provided in the food portion of the diet, the softer the faeces will be. Owners should be warned that any change in diet may result in transient soft faeces, but veterinary attention should be sought if this lasts for longer than 48 to 72 hours.
Enteritis can be caused by bacteria, fungi or yeasts, endoparasites and viral disease. Dysbiosis of the gastrointestinal tract can be triggered by drug use, stress or dietary changes. When true diarrhoea is seen, faecal cytology can be instrumental in helping to determine the underlying cause, alongside faecal parasitology, faecal culture and other ancillary testing (Chitty, 2018). A faecal Gram stain is a simple in-house test that can help identify abnormal bacterial and fungal elements or bacterial overgrowths. As a general rule, a faecal Gram stain of a parrot should contain approximately 70 percent Gram-positive rods, 25 percent Gram-positive cocci and scattered Gram-positive bacteria and yeasts (Chitty, 2018).
When true diarrhoea is seen, faecal cytology can be instrumental in helping to determine the underlying cause
Excessive yeast in a faecal sample, or evidence of budding, can be an indicator of candidiasis. This is caused when Candida albicans, a normal component of gastrointestinal flora, grows excessively. Candidiasis is often triggered in young birds that have yet to develop fully functional immune systems or by immunosuppression, recent antibiotic use and poor hygiene in a bird’s housing (Doneley, 2016b). Another common cause of diarrhoea in pet parrots that can be identified via faecal cytology is Macrorhabdus ornithogaster. Though previously referred to as “megabacteria”, M. ornithogaster is actually an ascomycetous yeast that is seen as a long filamentous Gram-positive organism on faecal cytology (Figure 4). This organism is commonly reported in budgerigars but has been identified in many other parrot species (Doneley, 2016b).
Parasitic and bacterial enteritis
Parasitic enteritis is uncommon but should be considered in new and free-flighted parrots or those who live in outdoor aviaries. Faecal flotation with zinc sulfate or wet preparation slides can help with the identification of diarrhoea-causing endoparasites (Figure 5). Bacterial enteritis can be caused by dysbiosis or by one of several communicable bacteria, including Salmonella spp., Escherichia coli, Enterobacter spp., Pseudomonas spp. and Aeromonas spp. (Sandmeier, 2016). If bacterial enteritis is suspected, it is important to evaluate husbandry and hygiene to identify if there may be an underlying cause. Faecal culture carried out concurrently with faecal cytology can help with diagnosis of bacterial enteritis. Treatment should be appropriate and based on culture results.
Psittacosis is a common bacterial disease in companion parrots that is caused by Chlamydophila psittaci. While common presenting signs include dyspnoea, ocular and nasal discharge, ruffled feathers and anorexia, yellow or green diarrhoea is often observed as a clinical sign (Lierz, 2005). Psittacosis is of particular importance due to its long latency period and highly infectious and zoonotic nature. In many cases, birds are silent carriers of the disease and can shed intermittently, infecting other parrots they come in contact with.
A diagnosis of psittacosis can be based on serology, PCR of tissue, ocular or nasal secretions or faeces, and radiographic changes, such as air sacculitis and splenomegaly (Lierz, 2005). However, it is important to understand that false negatives occur during testing and birds with positive serology may not be infective if they have cleared the disease. Treatment is relatively straightforward with the use of tetracyclines and supportive care for other symptoms. While psittacosis is not a notifiable disease in the United Kingdom, it is in several other countries where there can be strict rules governing the treatment of psittacosis.
Proventricular dilatation disease
Proventricular dilatation disease (PDD) can be a cause for dropping changes and diarrhoea in parrots. It is caused by avian bornavirus and is the most common cause of proventricular disease in companion parrots (Sandmeier, 2016). Common symptoms include undigested seed in the faeces, diarrhoea, vomiting and/or regurgitation, weight loss and emaciation. As the disease progresses, affected birds can show ataxia, tremors and weakness. The virus is transmitted horizontally between birds, either during rearing or during mixing events such as being brought to a pet shop for sale. The incubation period can be up to three months in adult birds (Doneley, 2016b).
Radiographs of PDD-affected birds will show a severely distended proventriculus, which can be confirmed with contrast radiography or fluoroscopy
Radiographs of PDD-affected birds will show a severely distended proventriculus, which can be confirmed with contrast radiography or fluoroscopy. Diagnosis can be confirmed by a combination of methods, including serology and PCR, but a definitive diagnosis can be achieved via a histopathological analysis of a crop biopsy sample that includes a section of nerve. This reveals a non-suppurative lymphoplasmacytic ganglioneuritis of nerve tissue (Doneley, 2016b). Unfortunately, treatment options are limited. The use of celecoxib has been advocated (Hoppes and Shivaprasad, 2020); however, a study by Escandon et al. (2019) has failed to replicate these results. Adjunctive therapies include the use of prokinetic drugs such as metoclopramide and cisapride, but the disease is ultimately fatal.
When investigating diarrhoea in pet parrots, the first step is to determine if true diarrhoea is present. Following this, appropriate screening tools such as faecal cytology and culture should be employed to determine the underlying cause of the diarrhoea. Some cases of diarrhoea may be transient and related to diet or dietary changes, whereas other cases may be caused by an underlying disease process.