Meningoencephalitis and other conditions associated with Histophilus ovis infection in sheep

Abstract

Histophilus ovis was isolated from 29 sheep in 20 flocks and 2 artificial insemination (AI) centres in southern New South Wales from 1984 to 1990. The clinical and pathological findings were consistent with previous reports and included polyarthritis (7 flocks), epididymo-orchitis (5), meningoencephalitis (3), pneumonia (3), septicaemia (2), mastitis (1) and metritis (1). Six sheep had meningoencephalitis, a syndrome not previously associated with H ovis infection in sheep, which was similar pathologically to thromboembolic meningoencephalitis in cattle, caused by the related organism, Haemophilus somnus. H ovis was isolated from the semen of 12-month-old rams in a flock that had polyarthritis due to H ovis, in 4-month-old ram lambs and from the uterus of a ewe in a flock that had sporadic cases of H ovis septicaemia.

Histophilosis as a Natural Disease

“…Other presentations are abortion, generalized pyemia, metritis, mastitis, and TME. Histophilosis tends to affect lambs, with polyarthritis in younger (1-4 weeks) and septicemia in older animals (4-7 months) (Philbey et al 1991). Disease can occur as outbreaks.…”

“…Neurological disease occurs in some episodes, affecting both lambs and adults. As in cattle, CNS disease may occur as TME, or as suppurative leptomeningitis-ventriculitis-choroiditis (Philbey et al 1991). The means of transmission is unknown.…”

“…Spontaneous abortion due to H. somni appears to be rare in sheep (Kirkbride 1993b), but has been reported as a result of polymicrobial infection that includes H. somni (Hajtós 1987). CNS disease in sheep, as in cattle, occurs in two forms: a TME-like syndrome, essentially indistinguishable from the bovine disease, and suppurative leptomeningitisventriculitis-choroiditis, particularly in lambs that survive an initial episode of septicemia (Kennedy et al 1958;Philbey et al 1991;Romero et al 2013). The distinctive relationship that occurs in cattle between microvascular endothelium and flat adherent colonies of H. somni can also be seen microscopically in the brains of sheep (Cassidy et al 1997).…”

Acquisition of haemoglobin-bound iron by Histophilus somni

“…H. somni is a fastidious and slow-growing organism with low biochemical activity. H. somni is associated with a variety of conditions such as septicaemia, myocarditis, arthritis, pyaemia, mastitis, metritis, abortion, neonatal mortality, decreased fertility in ewes and rams, epididymo-orchitis, pneumo nia and thrombotic meningoencephalitis (Robert, 1956;Rahaley and White, 1977;Rahaley, 1978a;Webb, 1983b;Harris and Janzen, 1989;Philbey et al 1991;Cassidy et al, 1997). H. somni has aIso been iso lated from the vagina and vaginal fluids of c1inicaUy normal ewes (Rahaley, 1978b;Higgins et al, 1981;Harris and Janzen, 1989) and it has been suggested that the genital (Webb, 1983b) and respiratory (Philbey et al, 1991) tracts are the natural habitats of H. somni.…”

Isolation of Histophilus somni from the nasal exudates of a clinically healthy adult goat

“…Other signs of the septicemic form are myocarditis (Haines et al 2004), otitis (Duarte and Hamdan 2004), mastitis (Armstrong et al 1986), conjunctivitis, and polyarthritis. In ovines, its participation has been reported in orchitis, epididimitis, mastitis (Palomares et al 2005), abortion (McDowell et al 1994, synovitis, meningoencephalitis (Philbey et al 1991;Cassidy et al 1997), septicemia, and pneumonia (Kearney and Orr 1993).…”