Hypophosphataemia and anaemia in an alpaca
Janice Thompson: BVSc, PhD, Clinical Pathologist, Gribbles Veterinary Pathology, Palmerston North, New Zealand
History and clinical examination
An alpaca of unreported age and sex showed weight loss and depression for 2 weeks and eventually became quite thin. It eventually spent most of its time recumbent although did rise to eat. The owner drenched it with ivomec, and it was given a Vitamin B 12 injection. An in-house (clinic) FEC later revealed 700 epg, although the alpaca had been drenched 5 days previously.
On clinical examination no abnormalities were detected.
Blood was taken for routine haematological and biochemical examination.
Blood smear comments
Moderate anisocytosis present. Mild polychromasia present. Moderate numbers of dacrocytes present. Small numbers of microcytes present. Leucocytes appear normal morphologically.
Findings from the clinical pathological examination
There was a moderate poorly regenerative anaemia. The numbers of NRBCs were inappropriately high relative to the numbers of reticulocytes.
There was an inflammatory leucogram with the mature neutrophilia indicating ongoing inflammation although fibrinogen was normal.
There was a severe hypophosphataemia.
The serum GDH concentration increase was non significant.
An interpretation of Diagnostic Exercise No. 17
In this animal, the hypophosphataemia may have arisen from either parasitism, and despite drenching there were still large numbers of eggs counted in a faecal sample, or it may have arisen from decreased availability or decreased intestinal absorption from the pasture as a result of other causes/ mechanisms.
The anaemia may have arisen from a number of mechanisms. Severe hypophosphataemia in other species (eg cats, dogs, humans) may cause a haemolytic anaemia because phosphorus is needed for the formation of ATP and this is required for the maintenance of RBC shape and function. This has not been reported in alpacas but should still be considered as a differential. Anaemia may also arise from chronic disease/ inflammation/ bone marrow suppression or recent haemorrhage. Chronic disease was demonstrated in this animal by the inflammatory leucogram. There was no hypoproteinaemia or clinical signs to suggest recent haemorrhage. Most anaemias in alpacas have been described as non regenerative and associated with chronic disease and dacrocytes have been described in alpacas with iron deficiency anaemia but may also be normal in camelids.
In New Zealand, hypophosphataemia may occur in alpacas possibly as a result of Vitamin D deficiency. In prior New Zealand studies, serum phosphorus concentrations of alpacas showed a decline over June/July (ie mid winter) even despite adequate levels in the pasture. In addition to the hypophosphataemia, a mild hypocalcaemia was also seen in these studies. The active form of Vitamin D stimulates the absorption of phosphorus from the intestine and deficiency may result in hypophosphataemia. Rickets associated with hypophosphataemia has been diagnosed in alpacas in New Zealand and the USA. Alpacas have a thick fleece over winter and it is hypothesized that there may be decreased solar/ UV light induced synthesis of the active form of Vitamin D over winter. Vitamin D responsive rickets has been reported in young sheep in Southland, New Zealand during the winter. Alpacas originate from the Andes at an altitude where solar irradiation is intense, and it is hypothesized that the thick fleece may have arisen partly as a protective mechanism to prevent excessive amounts of UV radiation from reaching the skin, as well as for thermal protection against the cold. At the much lower altitudes in New Zealand, the thick fleece may prevent adequate skin irradiation necessary for active dermal Vitamin D synthesis. Vitamin D deficiency has been associated with rickets in housed cattle in the Northern Hemisphere, where obviously the cattle are not exposed to UV light.
Examination of the bones from young affected animals with severe hypophosphataemia in prior studies showed histological features of rickets. Bones from adult affected animals were not examined histologically in the prior study. The adult disease equivalent to rickets in young animals with active growth plates is osteomalacia. Clinically affected animals showed weight loss, abnormal gaits, tended to remain recumbent, and there were painful responses to manipulation of the limbs. Some had noticeably flattened rib cages. Recumbency and reluctance to move were a result of bone pain, and inflammatory changes within the bones may cause an inflammatory response when haematological examination is carried out. Alpacas with hypophosphataemia that showed the above clinical signs and that were treated with oral Vitamin D and monosodium phosphate recovered. It is also recommended that as a preventative measure, affected alpacas are shorn before winter.
Grace ND. Phosphorus. In: Grace ND (ed) The mineral requirements of grazing ruminants. Occasional publication 9. Pp 106-111. New Zealand Society of Animal Production, Hamilton, 1983.
Garry, F, Weiser MG, Belknap E. Clinical pathology of Llamas. Veterinary Clinics of North America: Food Animal Practice 10, 201-209, 1994.
Hill, FI, Thompson KG, Grace ND. Rickets in alpacas (Lama pacos) in New Zealand. New Zealand Veterinary Journal 42, 229-232, 1994.