Seasonal variations in the immune system of lower vertebrates

Zapata, A.; Varas, Alberto; Torroba, M.

doi:10.1016/0167-5699(92)90112-k

Cited by 244 publications

(147 citation statements)

References 30 publications

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“…Further studies should examine the responses of females in early gestation: however the confounding effect of season upon plasma corticosterone concentrations and upon leucocyte numbers (Zapata et al, 1992) would need to be considered in comparing such females with postpartum or vitellogenic females.…”

Section: Discussionmentioning

confidence: 99%

“…Wojtaszek, 1992) and other measures of immune function that may reflect season al changes in circulating corticosteroids (Saad and El Ridi, 1988;Zapata et al, 1992). For example, in the lizard Chalcides ocellatus, increases in plasma corticosterone concentrations during the winter months were associated with lysis of splenic T and B lymphocytes, while injecting "summer" lizards with corticosterone resulted in similar reductions in lymphocyte numbers (Saad and El Ridi, 1988).…”

Section: Introductionmentioning

confidence: 99%

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Adrenal and white cell count responses to chronic stress in gestating and postpartum females of the viviparous skink Egernia whitii (Scincidae)

Cartledge

Gartrell

Jones

2005

Comparative Biochemistry and Physiology Part A: Molecular &

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Adrenal and white cell count responses to chronic stress in gestating and postpartum females of the viviparous skink Egernia whitii (Scincidae)

Cartledge

Gartrell

Jones

2005

Comparative Biochemistry and Physiology Part A: Molecular &

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“…Laird (1950) considered intraleukocytic forms of Ht to be parasites phagocytized by leukocytes as part of an immune response in the vertebrate host. The activity of vertebrate immune systems varies seasonally (Martin (Zapata et al, 1992), being less active at lower temperatures (Hildemann, 1962;Wright and Cooper, 1981). This could explain the increase in the proportion of intraleukocytic parasites between September and November, as the temperature increases from a mean daily maximum of 12.2 C in September to 15.1 C in November during the austral spring (data from National Institute for Water and Atmospheric Research; NIWA).…”

Section: Spatial and Temporal Variation In Htmentioning

confidence: 99%

Ecology and Dynamics of the Blood Parasite, Hepatozoon Tuatarae (Apicomplexa), in Tuatara (Sphenodon Punctatus) on Stephens Island, New Zealand

Godfrey

Nelson

Bull

2011

Journal of Wildlife Diseases

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ABSTRACT:We explored infection patterns and temporal dynamics of the protozoan blood parasite Hepatozoon tuatarae (Apicomplexa) infecting the tuatara (Sphenodon punctatus), a protected reptile living on Stephens Island, New Zealand. In March 2006, we surveyed tuatara in five study sites to examine spatial variation in infection prevalence, and four times, from May 2005 to November 2006, we recaptured marked individuals within three study sites to examine the temporal dynamics of infection. We also examined how blood-parasite infection patterns were influenced by host sex, body size, and host infestation with ticks (Amblyomma sphenodonti) and mites (Neotrombicula spp.), which are potential vectors of the blood parasite. Infection prevalence (16.9-24% infected) and intensity (,0.01-0.1% blood cells infected) were low in all samples. Infection intensity varied among the five sampled sites in March 2006, but prevalence did not. Neither infection prevalence nor intensity varied with time, and infections were detected in consecutive samples from recaptured individuals for up to 18 mo. Neither survey showed an influence of host sex on infection, but both surveys showed infection intensity declined with increasing host body size, as did infection prevalence in the spatial survey. In the temporal survey, we found a positive relationship between the tick numbers on hosts and blood-parasite infection intensity, which were stronger in two of the sampling periods and among larger hosts. These data suggest that exposure and susceptibility to infection decreases with host size and that ticks, but not mites, are probably the vectors in this ancient host-parasite association of a long-lived (.50 yr) host.

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“…Even when they were maintained in an active state in a thermoregulated environment and not hibernated, the thymi regressed. Toads have lower humoral responses to heterologous erythrocytes in the summer and autumn as compared to the spring and summer (Zapata et al, 1992). Thus, an increased mortality in the fall may have occurred due to this seasonal variation in the toad's immune system.…”

Section: Discussionmentioning

confidence: 99%

“…Some facilities did not hibernate all toads and some elected to hibernate toads for periods as short as 4 wk. There is some evidence to support seasonal variation in the immune system of amphibians (Zapata et al, 1992). In frogs, maximal development of the thymus occurs in the summer with marked regression as winter approaches.…”

Section: Discussionmentioning

confidence: 99%

Causes of Mortality of the Wyoming Toad

Taylor

Williams

Thorne

et al. 1999

Journal of Wildlife Diseases

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Wyoming toads (Bufo baxteri) that died from January 1989 to June 1996 were submitted to the Wyoming State Veterinary Laboratory (Laramie, Wyoming, USA) for postmortem evaluation. These consisted of 108 free-ranging toads and 170 animals from six captive populations. Ninety seven (90%) of 108 free-ranging toad carcasses were submitted during September and October. From 1989 to 1992, 27 (77%) of 35 mortalities in the captive populations occurred in October, November, and December. From 1993 to 1996, mortality in captive toads occurred without a seasonal pattern and coincided with changes in hibernation protocols that no longer mimicked natural cycles. Cause of mortality was determined in 147 (53%) of the 278 cases. Mycotic dermatitis with secondary bacterial septicemia was the most frequent diagnosis in 104 (71%) of 147 toads. Basidiobolus ranarum was found by microscopic examination of skin sections in 100 (96%) of 104 of these mortalities. This fungus was isolated from 30 (56%) of 54 freeranging and 24 (48%) of 50 captive toads. This research documents the causes of mortality for both free-ranging and captive endangered Wyoming toads over a 7 yr period.

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Seasonal variations in the immune system of lower vertebrates

Cited by 244 publications

References 30 publications

Adrenal and white cell count responses to chronic stress in gestating and postpartum females of the viviparous skink Egernia whitii (Scincidae)

Adrenal and white cell count responses to chronic stress in gestating and postpartum females of the viviparous skink Egernia whitii (Scincidae)

Ecology and Dynamics of the Blood Parasite, Hepatozoon Tuatarae (Apicomplexa), in Tuatara (Sphenodon Punctatus) on Stephens Island, New Zealand

Causes of Mortality of the Wyoming Toad

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