Further studies in the use of monensin in the control of experimental ovine toxoplasmosis

Buxton, D.; Blewett, David A.; Trees, A. J.; McColgan, Christina; Finlayson, J.

doi:10.1016/0021-9975(88)90021-7

Cited by 80 publications

(46 citation statements)

References 16 publications

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“…In none of the cases were malformations of the CNS noticed during post mortem analysis. Furthermore, in numerous studies where pregnant sheep were also orally infected with sporulated oocysts and showed similar episodes of fever, developing body temperatures higher than 41°, the occurrence of acute phase abortions was not described in any of them [5,16-18]. According to these results, it can be concluded that hyperthermia alone is unlikely to be the cause of acute phase abortions in toxoplasmosis.…”

Section: Discussionmentioning

confidence: 96%

“…The dose administered at day 90 of gestation (2000 sporulated oocysts), has been previously used in several studies without the occurrence of acute phase abortions [16,18-20]; however, acute phase abortions were recorded in other studies using the same dose [7,8]. A recent study employed a higher dose of oocysts (3000) of the same isolate (M4) without finding any acute phase abortion [21], also suggesting that the isolate used in this experimental inoculation was not especially virulent.…”

Section: Discussionmentioning

confidence: 99%

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Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep

Castaño

Fuertes

Ferre

et al. 2014

Vet Res

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After oral administration of ewes during mid gestation with 2000 freshly prepared sporulated oocysts of T. gondii isolate M4, abortions occurred between days 7 and 11 in 91.6% of pregnant and infected ewes. Afterwards, a further infection was carried out at late gestation in another group of sheep with 500 sporulated oocysts. Abortions happened again between days 9 and 11 post infection (pi) in 58.3% of the infected ewes. Classically, abortions in natural and experimental ovine toxoplasmosis usually occur one month after infection. Few experimental studies have reported the so-called acute phase abortions as early as 7 to 14 days after oral inoculation of oocysts, and pyrexia was proposed to be responsible for abortion, although the underline mechanism was not elucidated. In the present study, all placentas analysed from ewes suffering acute phase abortions showed infarcts and thrombosis in the caruncullar villi of the placentomes and ischemic lesions (periventricular leukomalacia) in the brain of some foetuses. The parasite was identified by PCR in samples from some placentomes of only one sheep, and no antigen was detected by immunohistochemical labelling. These findings suggest that the vascular lesions found in the placenta, and the consequent hypoxic damage to the foetus, could be associated to the occurrence of acute phase abortions. Although the pathogenesis of these lesions remains to be determined, the infectious dose or virulence of the isolate may play a role in their development.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep

Castaño

Fuertes

Ferre

et al. 2014

Vet Res

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“…An ELISA was used to detect IgG antibodies to T. gondii in sheep sera as described by Buxton and colleagues [24]. This ELISA used a water-soluble antigen fraction of T. gondii tachyzoites of the S48 strain [25].…”

Section: Methodsmentioning

confidence: 99%

“…Data was expressed as percentage positivity in comparison to a standard, high titre, positive control serum obtained from an experimentally infected animal. Optical density (OD) readings, resulting in a percentage positivity under 25% were considered to be negative; percentage positivity values of 25% and under 30% were classified as borderline and percentage positivity values of 30% and above were interpreted as positive [24]. Sera were tested in duplicate and results that did not match or borderline results were repeated.…”

Section: Methodsmentioning

confidence: 99%

Increased Toxoplasma gondii positivity relative to age in 125 Scottish sheep flocks; evidence of frequent acquired infection

Katzer

Brülisauer

Collantes-Fernández

et al. 2011

Vet Res

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Toxoplasma gondii seroprevalence was determined in 3333 sheep sera from 125 distinct sheep flocks in Scotland, with the majority of flocks being represented by 27 samples, which were collected between July 2006 and August 2008. The selected farms give a representative sample of 14 400 sheep holdings identified in the Scottish Government census data from 2004. Overall T. gondii seroprevalence, at individual sheep level, was determined to be 56.6%; each flock tested, had at least a single positive animal and in four flocks all ewes tested positive. The seroprevalence of sheep increased from 37.7% in one year old stock to 73.8% in ewes that were older than six years, showing that acquired infections during the life of the animals is frequent and that environmental contamination by T. gondii oocysts must be significant. The median within-flock seroprevalence varied significantly across Scotland, with the lowest seroprevalence of 42.3% in the South and the highest seroprevalence of 69.2% in the far North of Scotland and the Scottish Islands, while the central part of Scotland had a seroprevalence of 57.7%. This distribution disequilibrium may be due to the spread and survival of oocysts on pasture and lambing areas. A questionnaire accompanying sampling of flocks identified farms that used Toxovax®, a commercial vaccine that protects sheep from abortion due to T. gondii infection. Only 24.7% of farmers used the vaccine and the vaccine did not significantly affect the within flock seroprevalence for T. gondii. The implications for food safety and human infection are discussed.

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“…Monensin has been used for the control of toxoplasmosis in pregnant sheep (Buxton et al, 1988), disseminated visceral coccidiosis in cranes (Carpenter and Novilla, 1992), diarrheal disease in swine (Kyriakis et al, 1993), gregarine infections in shrimp (Jones et al, 1994;Fajer-Avila et al, 2005) and microsporidial gill disease in fish (Becker et al, 2002). The use of monensin to improve efficiency of milk production in dairy cattle has been approved in the U.S. (FDA, 2004).…”

Section: Introductionmentioning

confidence: 97%

Ionophores

Novilla¹

2012

Veterinary Toxicology

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Further studies in the use of monensin in the control of experimental ovine toxoplasmosis

Cited by 80 publications

References 16 publications

Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep

Placental thrombosis in acute phase abortions during experimental Toxoplasma gondii infection in sheep

Increased Toxoplasma gondii positivity relative to age in 125 Scottish sheep flocks; evidence of frequent acquired infection

Ionophores

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