Metabolic and Nutritional Diseases in Wild Animals

Metabolic and nutritional diseases in wild animals mean the diseases that occur due to the “imbalance between the rate of ‘input’ of dietary nutrients and the ‘output’ of products (product like new born, milk for young one etc.) and lead to the occurrence of metabolic derangements in the affected wild animal species.

Rickets and Osteoporosis

Rickets occurs due to malformation of the growing bone (bowing of limbs/curving in limbs) due to lack of vitamin D3 and there is a failure of hardening of bone.

In case of rickets, the mineralization and mineral absorption are not in a match.

Osteoporosis occurs in both the adults and juveniles (but may be frequent in senile female reptiles), where the already hardened bones become weakened by the withdrawal of calcium for metabolic purposes and the wild animals become more prone for the development of fractures.

This is a condition of bone wherein there is more resorption of osteoid than the deposition of new tissue.

Hence, there is reduction in the organic matrix of bone. Protein deficiency also may have some influencing effect on the occurrence of osteoporosis.

Osteomalacia and Fibrous Osteodystrophy

These disorders are often seen in the young hatchlings of crocodiles which subsequently reveal failure of hardening of bones due to lack of calcium.

Among mammals, bone eaters (eg. hyaena) if deprived of bones during feeding (like hyaenas) will end up in metabolic bone diseases.

Etiology

• Feeding diet with less calcium (provision of mince with liver and heart without bone or with less bones).
• Failure in proper absorption of calcium (diseases of GI tract / excessive phosphorus in diet).
• Insufficient calcium supplement and hormonal imbalances due to multiple causes.
• Lack of vitamin D esp. in indoor-kept wild animals.
• Prolonged storage of ration leads to less vitamin D3.

Clinical signs

Crocodiles get often affected by the metabolic bone diseases. The clinical signs are:

• Persisting of kyphokoliosis (hunch backed appearance) esp. in subadults and adult crocodiles.
• Weakness of hatchling to walk on land while they still can move freely if in water or can swim freely in water.
• Falling of teeth and poor calcification of teeth.
• Jaw bones become more pliable as evidenced in case of hatchlings (rubber jaws) Weakness in hatchlings along with sluggish movements.
• Teeth becomes diaphanous like shards of glass (glassy teeth).
• In chelonians, lump like appearance of carapace (compare with normal nearby chelonian).

Diagnosis

Serum estimation of calcium and phosphorus in addition to the radiographical examination and clinical signs and history of feeding and management.

Note: In this context, it is to be remembered that especially in the periods of production of egg shells, the calcium mobilization from bones is at peak and hence, the reptiles when hypocalcemic during these periods will have difficulties in maintaining muscular tonicity and as a result, prolapse of uterus may occur in crocodiles.

Hence, whenever prolapse occurs in crocodiles or any reptiles, correlation with the metabolic derangements of calcium need to be paid attention.

Metabolic Bone Disease in Captive Aviary Species

Rickets is encountered in growing birds especially in birds which have long or large legs and is caused by Ca and Ph. Imbalance and deficiency of vitamin D. But osteomalacia is a disease of adult birds and causes are same as the previous ones.

Clinical signs

• Weakness, anorexia, polydipsia, intermittent loose droppings.
• Poor feather growth and chewing at plumage.
• Hunch backed appearance if thoracic cage reveals collapse.
• Upper and lower beaks may not oppose each other properly and prehension of  food is faulty.
• Hyperaesthetic and reveal muscle spasms.
• Improper calcification of eggs (eggs become more soft).
• Retention of eggs without laying due to lack of calcium.

Gout

Gout condition is more common in captive birds and reptiles in particular.

Among the aviary species, especially raptors like hawks, eagles, kites, vultures, falcons are highly susceptible in addition to ostrich, cassowary, peafowls, budgerigars, love birds, parakeets, cormorant, goose, duck etc.

Broader classification and the specific classification of gout should be known for a good understanding about this disorder.

Broader Classification of Gout

• True gout: Deposition of monosodium urate crystals.
• Pseudo gout: This is formed by deposition of any crystal other than sodium urate.

Specific Classification of Gout

Note: Both the articular form and the visceral form of gout are the clinical forms of same problem (gout).

Perhapes, in case of articular gout, tissue reaction is there by swelling (tophi is present).

In visceral form, though some urate crystals may get deposited on synovial membranes of joints, there is no tissue reaction at the joints.

Etiology

Renal problems (infection/inflammation/renal lesions due to nephrotoxic substances like gentamicin and anti-inflammatory drugs like salicylates, probenecids, phenylbutazone etc.) are the basic cause because liver and esp. the renal tissues are involved in production of urate crystals.

Nutrition (increased protein intake with provision of water, increased protein intake without provision of water or incorrect balance of aminoacids in the feed).

Stress leading to dehydration or dehydration due to diseases all lead ultimately reduced renal blood flow and thereby renal efficiency is lots and ultimately gout occurs.

Congenital causes might be the causal factors as documented in case of nile crocodile hatchlings.

Clinical Signs and Diagnosis

Elevated serum uric acid helps the diagnosis in general, in addition to the specific examination for urate crystals in joints.

In crocodiles or lizards or chelonians affected by gout, general depression is there but antemortem-diagnosis is difficult in visceral gout.

In articular gout, the affected leg joints become painful and the animal is reluctant to move.

In advanced arthritic gout, the swollen joints can be easily seen or palpated.

In captive aviary species, affected by visceral gout, antemortem- diagnosis is difficult as in case of many species.

In articular gout, urate tophi may be seen esp. in advanced cases (seen as whitish areas at joints).

Note: The signs of articular gout often are confused with bumble foot (Muroxide test helps to confirm uric acid crystals and in this test, take one drop of nitric acid on a clean slide and mix it with the crystals aspirated from a urate typhus and slowly flame it till this becomes dry and cool. Now, add one drop of ammonia and presence of a reddish-purple color will indicate the presence of uric acid.

In raptors or other aviary species, when you ventral surface of digits, uniform swelling may be seen in entire digits of both the limbs and of course and experienced zoo veterinarians will naturally try to differentiate the perch based problems or lesions, in these aviary species reared under captive conditions.

Hypothyroidism

Hypothyroidism in Captive Wild Mammals

Hypothyroidism may occur in any species of wild mammals.

Clinical signs

Obesity, alopecia, dullness with lethargic movements and lowered serum cholesterol are the major features in this hypothyroidism.

Hypothyroidism in captive aviary species (documented in budgerigars etc.)

Goiter in birds due to iodine deficiency may lead to hypothyroidism because the iodine is a must for the development of thyroid gland.

Due to iodine deficiency, there may be hypertrophy of thyroid gland resulting in goiter.

Clinical signs

The affected birds will reveal change of voice i.e. a respiratory noise heard as a characteristic ‘click’ and this is due to the pressure of the enlarged thyroid on syrinx and the lower trachea.

In addition to the obesity and dullness, there may be ruffled feathers in the affected bird.

Diabetes Mellitus in Mammals and Birds

Differentiate insulin dependent diabetes mellitus from non-insulin dependent diabetes mellitus. Mostly, insulin dependent diabetes mellitus occurs. This condition is recorded in non-human primates in particular.(polyuria, polydipsia, polyphagia and glycosuria in addition to the dullness, anorexia, unconsciousness in extreme stages and staggering may be noticed in the affected animals)

Other mammals may also get affected by this condition. However, this needs a more detailed but a specific study esp. in case of aged wild animal species.

Further, this condition has been documented in case of captive birds also (ruffled feathers, polyuria, polydipsia, polyphagia, glycosuria and weakness are the consistent clinical signs in the affected birds).

Fatty Liver in Mammals and Birds

Fatty liver in mammals and birds may occur in captive mammals and aviary species like budgerigars (male budgerigars especially have increased incidences of fatty liver and multiple metabolic causes might be assigned as etiological factors.

Neonatal Hypoglycemia in Wild Animals

Neonatal hypoglycemia in wild animals occurs mainly due to insufficient intake of colostrums or milk from mother due to multiple reasons and this causes metabolic derangements and hypoglycemia occurs in the affected wild animal species.

Pale skin, weakness, recumbency, hypothermia, incoordination with terminal convulsions are the clinical signs revealed.

Monitoring the infant for proper feeding (ensure for proper energy intake) and monitoring of the mother on proper nursing may help for the prevention of this problem in case of wild animals.

Ketosis (Acetonemia) in Wild Ruminants

In ruminants whether it is domestic or wild (giraffe, deer, antelope, wild goat, wild sheep and wild bovid), the dietary carbohydrates are fermented in the rumen to short chain fatty acids (acetate in majority amount, propionate in moderate amount and butyrate in lesser amount). 

Hence, the glucose needs in these animal species are largely met by gluconeogenesis and it is to be understood that propionate and amino acids are the major precursors for gluconeogenesis.

Clinical Signs

In wasting form

Woody appearance of the animal due to apparent wasting and loss of cutaneous elasticity.

In nervous form (rule out rabies)

Animal walks in circles, head-pushing, apparent blindness, aimless walking, vigorous licking of objects and skin, depraved appetite, chewing movements with salivation.

Lactation Tetany in Wild Equids

Lactation tetany can be anticipated in case of wild equids reared under captive conditions. Zebras, wild asses and wild horses may get affected by this condition and often, it occurs in the lactating equids, either at about 10^th day, after giving birth or 1 to 2 days after the weaning of the young one for management reasons.

Even after the prolonged transport or after the severe exertion, this condition may occur.

Clinical Signs

• Stiff gait and the tail may be raised.
• Incoordination and tetany.
• Sweating in profuse manner.
• Rapid and labored respiration with wide dilatation of pupils which may be accompanied by a distinct thumping sound from the thorax due to spasmodic contraction of the diaphragm.
• Muscular fibrillation esp. of the masseter and shoulder region and trismus without prolapse of membrana nictitans unlike in tetanus disease.
• Reduced peristalsis and suspended urination and defecation.
• May attempt to drink but unable to swallow.
• Lowered calcium diet during the pre-stress period may help to avoid the excess gastro-intestinal absorption of calcium.

Parturitient Paresis (Milk Fever) in Wild Ruminants

Though there is no systematic study of this disease condition in wild cervids, this condition can be anticipated in the newly fawned deer or antelopes that have given birth. Especially when there are twin births, this can be anticipated. However, this can affect surely the gaur, mithun etc.

Milk fever condition commonly occurs within two days of parturition and this may also occur few weeks before or after the parturition.

Clinical signs

Hypothermia, dilated pupils, dry muzzle, suspended urination and defecation along with lethargic movements or dullness.

Weak heart sounds(rule out immobilization effects) and anorexia.

Diagnosis

Serum estimation of calcium helps to diagnose the condition.

Calcium Related Metabolic Derangements in Wild Birds

Other than bone related disease, some abnormalities are encountered in captive birds due to deranged calcium metabolism and are furnished below:

• Egg binding is commonly encountered in many aviary species and along with other causes, calcium deficiency due to multiple metabolic derangements play a significant role. Hence, in egg bound aviary species, calcium borogluconate is given by I/V or S/C route and this helps in the improvement of the tonicity of the musculatures and helps in the rapid expulsion of egg.
• Malformed egg esp. shell less egg or partially shelled egg or soft shelled egg may be laid by multiple aviary species reared under captive conditions. In addition to the salpingitis, the etiological factor for this might be the existence of imbalance in calcium and phosphorus levels.
• An imbalance in calcium, phosphorus and vitamin D is commonly encountered in parrots and the problem arises as a result of their customary diet of high oil-bearing foods such as sunflower and peanuts. This in addition to the metabolic derangements produce a variety of clinical expressions in the affected wild birds reared in captivity.

Colic as a Result of Metabolic Derangment

Colic is more commonly encountered in case of elephants in severe metabolic derangements like acidosis.

Feeding of unaccustomed food material, excess feeding of the routine food materials, obstruction anywhere in the gastro-intestinal tract and lesser exercise with non-provision of adequate amounts of water for the drinking purposes-all may precipitate the colic condition, in general.

Sings of Colic

• restlessness
• constipation
• depression
• disobedience or aggression
• absence of signs of health, in general.
• Acute abdomen is a non-infectious disease condition that can affect any wild animal species, in general. However, this problem is more encountered in case of llamas. Camelids often experience this problem.

Clinical Sings

• Dullness
• Temperature may be normal to sub-normal
• Anorexia
• Increased pulse and pain due to colic
• Normal to cyanotic mucosa
• Decreased defecation
• Decreased motility of stomach
• Increased respiration

Wounds, Abscesses and Injuries

Wounds, abscesses and injuries are very common among wild animal species especially in the captive ones. In-fighting is the common cause often.

Abscesses may occur if immediate treatment is not done due to multifaceted causes.

Long time persisting wounds are common among elephants in particular and routine treatment protocol needs to be adapted in all these cases.

In many captive animals, wounds may get further complicated by affections with maggots.