Dataset Information

Systemic Amyloid A Amyloidosis in Island Foxes (Urocyon littoralis): Severity and Risk Factors.

ABSTRACT: Systemic amyloid A (AA) amyloidosis is highly prevalent (34%) in endangered island foxes (Urocyon littoralis) and poses a risk to species recovery. Although elevated serum AA (SAA) from prolonged or recurrent inflammation predisposes to AA amyloidosis, additional risk factors are poorly understood. Here we define the severity of glomerular and medullary renal amyloid and identify risk factors for AA amyloidosis in 321 island foxes necropsied from 1987 through 2010. In affected kidneys, amyloid more commonly accumulated in the medullary interstitium than in the glomeruli (98% [n= 78 of 80] vs 56% [n= 45], respectively;P< .0001), and medullary deposition was more commonly severe (19% [n= 20 of 105]) as compared with glomeruli (7% [n= 7];P= .01). Univariate odds ratios (ORs) of severe renal AA amyloidosis were greater for short- and long-term captive foxes as compared with free-ranging foxes (ORs = 3.2, 3.7, respectively; overall P= .05) and for females as compared with males (OR = 2.9;P= .05). Multivariable logistic regression revealed that independent risk factors for amyloid development were increasing age class (OR = 3.8;P< .0001), San Clemente Island subspecies versus San Nicolas Island subspecies (OR = 5.3;P= .0003), captivity (OR = 5.1;P= .0001), and nephritis (OR = 2.3;P= .01). The increased risk associated with the San Clemente subspecies or captivity suggests roles for genetic as well as exogenous risk factors in the development of AA amyloidosis.

SUBMITTER: Gaffney PM

PROVIDER: S-EPMC4871602 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Publications

Systemic Amyloid A Amyloidosis in Island Foxes (Urocyon littoralis): Severity and Risk Factors.

Gaffney P M PM Witte C C Clifford D L DL Imai D M DM O'Brien T D TD Trejo M M Liberta F F Annamalai K K Fändrich M M Masliah E E Munson L L Sigurdson C J CJ

Veterinary pathology 20150929 3

Systemic amyloid A (AA) amyloidosis is highly prevalent (34%) in endangered island foxes (Urocyon littoralis) and poses a risk to species recovery. Although elevated serum AA (SAA) from prolonged or recurrent inflammation predisposes to AA amyloidosis, additional risk factors are poorly understood. Here we define the severity of glomerular and medullary renal amyloid and identify risk factors for AA amyloidosis in 321 island foxes necropsied from 1987 through 2010. In affected kidneys, amyloid m ...[more]

PMID: 26419399

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Project description:Disease transmission and epidemic prevention are top conservation concerns for wildlife managers, especially for small, isolated populations. Previous studies have shown that the course of an epidemic within a heterogeneous host population is strongly influenced by whether pathogens are introduced to regions of relatively high or low host densities. This raises the question of how disease monitoring and vaccination programs are influenced by spatial heterogeneity in host distributions. We addressed this question by modeling vaccination and monitoring strategies for the Channel Island fox (Urocyon littoralis), which has a history of substantial population decline due to introduced disease. We simulated various strategies to detect and prevent epidemics of rabies and canine distemper using a spatially explicit model, which was parameterized from field studies. Increasing sentinel monitoring frequency, and to a lesser degree, the number of monitored sentinels from 50 to 150 radio collared animals, reduced the time to epidemic detection and percentage of the fox population infected at the time of detection for both pathogens. Fox density at the location of pathogen introduction had little influence on the time to detection, but a large influence on how many foxes had become infected by the detection day, especially when sentinels were monitored relatively infrequently. The efficacy of different vaccination strategies was heavily influenced by local host density at the site of pathogen entry. Generally, creating a vaccine firewall far away from the site of pathogen entry was the least effective strategy. A firewall close to the site of pathogen entry was generally more effective than a random distribution of vaccinated animals when pathogens entered regions of high host density, but not when pathogens entered regions of low host density. These results highlight the importance of considering host densities at likely locations of pathogen invasion when designing disease management plans.

Project description:Diseases threaten wildlife populations worldwide and have caused severe declines resulting in host species being listed as threatened or endangered. The risk of a widespread epidemic is especially high when pathogens are introduced to naive host populations, often leading to high morbidity and mortality. Prevention and control of these epidemics is based on knowledge of what drives pathogen transmission among hosts. Previous disease outbreaks suggest the spread of directly transmitted pathogens is determined by host contact rates and local host density. While theoretical models of disease spread typically assume a constant host density, most wildlife populations occur at a variety of densities across the landscape. We explored how spatial heterogeneity in host density influences pathogen spread by simulating the introduction and spread of rabies and canine distemper in a spatially heterogeneous population of Channel Island foxes (Urocyon littoralis), coupling fox density and contact rates with probabilities of viral transmission. For both diseases, the outcome of pathogen introductions varied widely among simulation iterations and depended on the density of hosts at the site of pathogen introduction. Introductions into areas of higher fox densities resulted in more rapid pathogen transmission and greater impact on the host population than if the pathogen was introduced at lower densities. Both pathogens were extirpated in a substantial fraction of iterations. Rabies was over five times more likely to go locally extinct when introduced at low host density sites than at high host-density sites, leaving an average of >99% of foxes uninfected. Canine distemper went extinct in >98% of iterations regardless of introduction site, but only after >90% of foxes had become infected. Our results highlight the difficulty in predicting the course of an epidemic, in part due to complex interactions between pathogen biology and host behavior, exacerbated by the spatial variation of most host populations.

Dataset Information

Systemic Amyloid A Amyloidosis in Island Foxes (Urocyon littoralis): Severity and Risk Factors.

Publications

Systemic Amyloid A Amyloidosis in Island Foxes (Urocyon littoralis): Severity and Risk Factors.

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