Non-agreement between 2 serologic techniques for detecting antibody to Brucella ovis in naturally infected sheep.

Brucella ovis is the causative agent of ovine brucellosis, which is an important infectious disease in sheep farming worldwide and is responsible for economic losses because of its negative effect on the reproductive system of rams and ewes. Serologic tests are the main tools for detection of infection; however, these tests commonly yield a high frequency of false-negative results. We compared 2 serologic tests, agar gel immunodiffusion (AGID) and ELISA, for the detection of anti-B. ovis antibodies in naturally infected sheep. Of the 728 serum samples analyzed, 0.3% were positive by AGID and 9.2% by ELISA. Positive results were obtained for different animals and flocks. There was no statistical difference between the detection frequency of the 2 methods (p = 0.674), and the kappa test indicated low concordance (κ = 0.005). The lack of agreement between results obtained using AGID and ELISA, associated with the absence of clinical signs, makes it difficult to detect ovine brucellosis efficiently, and demonstrates the need for effective tests for the definitive detection of B. ovis infection.

Dysfunction of sensory nerves during attacks of hypokalemic periodic paralysis.

Reversible electrophysiologic abnormalities of sensory nerve function were found by chance in three patients with hypokalemic periodic paralysis, a disorder previously considered to affect the function of muscle membranes only. A formal, prospective study was therefore conducted. Serial nerve conduction studies were done in ten additional patients. Amplitude of sensory action potentials was significantly smaller during paralytic attacks, but did not differ from controls after normalization of serum potassium concentration. These apparently novel findings might be explained by previous electrodiagnostic studies either not involving the testing of sensory nerves at all, or not being repeated after recovery from an attack. Involvement of sensory nerves in hypokalemic periodic paralysis is suggested to arise through dorsal root ganglia having an incomplete blood-nerve barrier and sensory neurons being particularly vulnerable to derangements affecting nerve cell metabolism. Neuronal inexcitability is postulated to occur consequent upon possible inactivation of the sodium-potassium pump by the low concentration of extracellular potassium. In patients with acute areflexic limb weakness, the diagnosis of hypokalemic periodic paralysis should not be excluded by abnormal results of sensory nerve conduction studies.