Metabolic profile of foot and mouth disease stressed sheep in semi arid region

Foot-and-mouth disease (FMD) is an OIE listed and one of the most feared viral diseases of the livestock. The disease is highly contagious in cloven-footed animals, most prevalent in cattle and buffaloes followed by sheep and goats, whereas pigs acts as amplifiers. The FMD virus (FMDV) belongs to genus Aphthovirus of the family Picornaviridae and is classified into seven antigenically distinct serotypes i.e. O, A, C, SAT1, SAT2 SAT3, and

Asia1; and innumerable subtypes . In domestic animals it causes economic losses by decreasing the production, cost of treatment etc. Lameness is usually the first indication of FMD in sheep and goats. An affected animal develops fever, is reluctant to walk, vesicles develop in the interdigital cleft, on the heel bulb and on the coronary band. Vesicles also form in the mouth (on dental pad, hard palate, lips and gums) but they rupture easily.

MATERIALS AND METHODS

Experimental animals

Two groups of sheep were used, one group comprises of 20 naturally infected sheep with FMD virus and other group with 10 healthy sheep was kept as control. The animals were of local breed and both groups comprises of both Ram and Ewe. The animals were kept under free-range system with optimum maintenance requirement. Their feed consisted of a concentrate mixture provided for their optimal maintenance and Jowar (Sorgum) Kadbi or Green (Lucern or Maize) accordingly to the availability of fodder.

Collection of blood and separation of serum

Peripheral blood was collected by puncturing the jugular vein with the least stress to the animal under aseptic condition directly into sterile tubes. The serum was separated out on the same day by centrifuging at 2000 rpm for 15 min. The serum samples were stored at -20 ° C till further use.

Virus isolation:

FMD virus was isolated from the tongue epithelial samples taken in 50% buffered glycerol and was triturated and centrifuged at centrifuged at 3000 rpm for 15 min. The supernatent was collected and filtered through 0.22µm membrane filter and was inoculated in Baby hamster kidney cell line, BHK-21 CT (Clone Tubingen) grown in MEM (GIBCO) for the presence of cytopathic effect. Further, Serotyping was done by sandwitch ELISA using reference FMDV reference serotypes (vaccine strains) O, A and Asia1 procured from Central Laboratory of the Project Directorate on FMD, IVRI, Mukteswar-Kumaon, Uttrakhand, India.

Biochemical tests:

Blood glucose, total protein, albumin, urea, calcium, phosphorus, cholesterol levels and activity of AST, ALT and ALP of both experimental and controlled group was analyzed on IDEXX VetTest automated chemistry analyzer.

Statistical Analysis:

RESULTS

The mean values of the parameters studied are presented in the table- 1. FMD affected sheep had significantly increased concentration of glucose and phosphorus, the activity of AST was significantly higher. Further the concentration of total protein, albumin, urea, cholesterol and calcium was significantly lower. The activity of ALT, ALP and GGT was non significantly higher in FMD affected animals in comparison to control group.

Table 1 Comparison of various Serum biochemical parameters in the FMD affected sheep and Control groups

DISCUSSION

albumin and protein concentration may also be due to alteration in pancreatic β -cell function that might have developed during the clinical course of FMD as reported by Barboni, 1980.

The cholesterol level in FMD affected sheep was lower in present study. This could have been due to the cytokine induced alteration in energy metabolism, with lipids being released from adipose tissue. In this situation, a reduction in cholesterol rich very low density lipoprotein (VLDL) and low density lipoprotein (LDL)would be expected, with an increased ratio of VLDL and LDL to high density lipoprotein (HDL) (Kaneko 1997).

Thyroid hormone increases both the rate of cholesterol synthesis and the rate of its catabolism by the liver. In hypothyroidism condition, lipids and cholesterol catabolism are decreased to a lesser degree than the synthesis of the cholesterol. The effect of these changes, results in an increase in serum cholesterol (Kaneko 1997). In contrast to this, however, Lal 1981, found evidence indicative of hypothyroid activity in FMD affected cows; this author reported decreased protein bound iodine (PBI) values in FMD affected Thrparkar cows compared with the levels in healthy lactating cows. The low serum calcium level in the present study may be associated with inappetance and hypoproteinemia as reported by Kaneko, 1997. Therefore, in the study there was a significant decrease in serum protein level and severe anorexia in FMD sheep, which is the possible explanation for hypocalcemia observed. The higher phosphorus level in infected sheep might be due to rapid respiration, higher pulse rate, tissue oxidation and acidosis due to lack of excretion. Mullick 1949, reported high phosphorus and low calcium in FMD affected cattle than normal. The serum AST values significantly increase, whereas there was nonsignificant increase in ALT, ALP, and GGT activity in FMD affected sheep. The transaminase activity intimately related with the protein catabolism and subsequent production of ketoacids. Georgie 1973 suggested that corticosteroid accelerates the transaminase reaction thereby augment the process of gluconeogenesis. Higher rectal temperature due to fever in infected animal induces stress condition which might have accelerated the transaminase activity. Elitok 1999 reported that the blood glucose and AST were higher in infected cattle than in control.

CONCLUSION

The biochemical alteration indicates the development of pancreatic dysfunction in Foot and Mouth disease affected sheep with FMDV serotype O.