Comparative pathological and immunohistochemical features of sarcoptic mange in five sympatric wildlife species in Northern Spain

This study collects pathological information concerning sarcoptic mange in sympatric red deer, roe deer, chamois, wolf and red fox from Northern Spain, and discusses reported variations in the response from the different species against Sarcoptes scabiei. Wolf is the only studied species which shows prevalence of the hypersensitivity (alopecic) response to the detriment of the hyperkeratotic form, usually observed in ungulates and fox. The present work shows the use of immunohistochemistry as a valuable tool for the study and diagnosis of sarcoptic mange in those species whose immune response or stage of infestation limits the number of detectable mites, not an unusual difficulty faced when working with sarcoptic mange in wildlife species.     

Clinical Picture and Antibody Response to Experimental Sarcoptes scabiei var. vulpes Infection in Red Foxes (Vulpes vulpes)

Three red foxes (Vulpes vulpes) were experimentally infected with Sarcoptes scabiei isolated from a naturally infected wild red fox. A fourth red fox served as a control. The first signs of sarcoptic mange became evident on the 31st day post infection (dpi). The signs gradually increased thereafter and between dpi 49 and 77 characteristic lesions of hyperkeratosis developed. Two of the infected foxes developed severe sarcoptic mange, and one of these animals died on dpi 121. The third fox developed a chronic hyperkeratotic lesion on its back, at the site where the mites had been applied. On dpi 127 the surviving foxes were treated systemically with ivermectin, and within 4 weeks the skin lesions had healed except on the pinnae of one animal. Antibodies to S. scabiei var. vulpes were demonstrated in the infected foxes by an ELISA with which seroconversion was seen around 4 weeks post infection (wpi). Western blot analysis of sequential sera of the infected animals demonstrated antibody activity consistently after the 2nd wpi. The fourth, non-infected, fox did not show any skin lesions throughout the experimental period nor any specific antibodies to S. scabiei var. vulpes. kw|Keywords|k]sarcoptic mange; k]red fox; k]serodiagnosis; k]ELISA     

Demonstrating frequency-dependent transmission of sarcoptic mange in red foxes

Understanding the relationship between disease transmission and host density is essential for predicting disease spread and control. Using long-term data on sarcoptic mange in a red fox Vulpes vulpes population, we tested long-held assumptions of density- and frequency-dependent direct disease transmission. We also assessed the role of indirect transmission. Contrary to assumptions typical of epidemiological models, mange dynamics are better explained by frequency-dependent disease transmission than by density-dependent transmission in this canid. We found no support for indirect transmission. We present the first estimates of R₀ and age-specific transmission coefficients for mange in foxes. These parameters are important for managing this poorly understood but highly contagious and economically damaging disease.     

Survival and Cause-Specific Mortality of Red Foxes in Agricultural and Urban Areas of Illinois

Abstract: Range expansion and population increase by coyotes (Canis latrans), reduced hunting and trapping, and intensified agricultural practices in the Midwest have altered red fox (Vulpes vulpes) mortality, although relative impacts of these factors are unknown. We examined mortality causes and survival of red foxes in urban and rural agricultural areas of Illinois, using radio telemetry data from 335 foxes (Nov 1996 to May 2002). We used Akaike's Information Criterion to evaluate six survival models for foxes reflecting 1) environmental effects, 2) intrinsic effects, 3) temporal effects, 4) behavioral effects, 5) social effects, and 6) a global model. Environmental and intrinsic models of survival were optimal for adult foxes. Adult foxes with low (0-20%) and high (80-100%) percentages of row crops in their home ranges had higher survival than adults with moderate percentages (40-70%). Heavier adults at capture also survived better. A global model (all covariates) was optimal for juvenile foxes. Higher juvenile survival associated with larger litters, lower body fat, and reduced dispersal time. Yearly survival ranged from 0.18 for rural male juveniles to 0.44 for rural female adults. Adult survival rates (0.35) were 11% higher than juvenile survival rates (0.24). Yearly survival varied for urban foxes due to cyclic outbreaks of sarcoptic mange (Sarcoptes scabei). Thus, summer survival (May-Sep) of urban juveniles ranged from 0.10 (mange present) to 0.83 (no mange recorded). Mange was the most common (45% of all fatalities) source of mortality for urban foxes, followed by road kill (31%). We recorded only 4 mange fatalities (2%) for rural foxes. Rural foxes experienced low hunting mortality (7%) and equivalent road kill and coyote predation fatalities (40% each). Sources of mortality for midwestern foxes have dramatically changed since the 1970s when hunting was the major cause of mortality. Coyote predation has effectively replaced hunting mortality, and cyclic patterns of mange outbreaks in urban fox populations might indicate a dynamic source or sink relationship to surrounding rural fox populations. Absent mange, urban areas might provide refugia for red foxes where coyote populations persist at high densities in rural areas. Managers of sympatric urban and rural wildlife populations must understand survival dynamics influencing the population at the landscape level.     

Sarcoptic mange vulnerability in carnivores of the Białowieża Primeval Forest,Poland: underlying determinant factors

Sarcoptic mange caused by Sarcoptes scabiei, is a highly contagious worldwide mite infection responsible for epizootic skin disease in populations of wild and domestic mammals. It causes skin disorders that may lead to severe generalized skin disease (mange). We investigated the spread and dynamics of sarcoptic mange in one of the best preserved carnivore communities in the Bia?owie?a Primeval Forest over the last 20 years. Sarcoptic mange was found in 6 of 10 investigated species. The highest percentage of infected individuals was recorded in red foxes (19 %), European badgers (9 %), grey wolves (7 %), raccoon dogs (6 %), and stone martens (5 %). Other species were not infected (least weasel, American mink, European polecat, pine marten) or infected sporadically (Eurasian lynx––1 case). Rate of infection was correlated with the sum of ecological and behavioral features, which may increase the spread of infection. Outbreaks of sarcoptic mange occurred simultaneously in several species of carnivores, which indicates the occurrence of between species transmission. We found that the source of investigated individuals (trapped, culled and found dead) may influence the results of the analysis. Our study shows that in carnivore communities such as in Bia?owie?a Forest, numerous species may serve as a reservoir of the pathogen and favor its persistence in the environment. This study indicates that sociality and use of den sites are important factors affecting sarcoptic mange spread and prevalence in wild populations of carnivores.     

The impact of sarcoptic mange Sarcoptes scabiei on the British fox Vulpes vulpes population

• 1 Disease epizootics can significantly influence host population dynamics and the structure and functioning of ecological communities. Sarcoptic mange Sarcoptes scabiei has dramatically reduced red fox populations Vulpes vulpes in several countries, including Britain, although impacts on demographic processes are poorly understood. We review the literature on the impact of mange on red fox populations, assess its current distribution in Britain through a questionnaire survey and present new data on resultant demographic changes in foxes in Bristol, UK.
• 2 A mange epizootic in Sweden spread across the entire country in < 10 years resulting in a decline in fox density of up to 95%; density remained lowered for 15–20 years. In Spain, mange has been enzootic for > 75 years and is widely distributed; mange presence was negatively correlated with habitat quality.
• 3 Localized outbreaks have occurred sporadically in Britain during the last 100 years. The most recent large‐scale outbreak arose in the 1990s, although mange has been present in south London and surrounding environs since the 1940s. The questionnaire survey indicated that mange was broadly distributed across Britain, but areas of perceived high prevalence (> 50% affected) were mainly in central and southern England. Habitat type did not significantly affect the presence/absence of mange or perceived prevalence rates. Subjective assessments suggested that populations take 15–20 years to recover.
• 4 Mange appeared in Bristol's foxes in 1994. During the epizootic phase (1994–95), mange spread through the city at a rate of 0.6–0.9 km/month, with a rise in infection in domestic dogs Canis familiaris c. 1–2 months later. Juvenile and adult fox mortality increased and the proportion of females that reproduced declined but litter size was unaffected. Population density declined by > 95%.
• 5 In the enzootic phase (1996–present), mange was the most significant mortality factor. Juvenile mortality was significantly higher than in the pre‐mange period, and the number of juveniles classified as dispersers declined. Mange infection reduced the reproductive potential of males and females: females with advanced mange did not breed; severely infected males failed to undergo spermatogenesis. In 2004, Bristol fox population density was only 15% of that in 1994.

     

Cycles in voles and small game in relation to variations in plant production indices in Northern Sweden

Population dynamics for voles (Cricetidae), Tengmalm's owl (Aegolius funereus (L.)), red fox (Vulpes vulpes (L.)) willow grouse (Lagopus lagopus (L.)), black grouse (Lyrurus tetrix (L.)), capercaillie (Tetrao urogallus L.), hazel hen (Tetrastes bonasia (L.)), mountain hare (Lepus timidus L.) and tularemia (Francisella tularensis (McCoy & Chapin)) and game bird recruitment were studied by index methods in northern Sweden. In addition contemporary temperature records and spruce (Picea abies (L.) Karst.) and pine (Pinus silvestris L.) cone crops (as indices for plant production) and the occurrence of forest damage, caused by voles eating bark, were studied.During 1970–80 two synchronous 4-year cycles were observed for voles, predators (Tengmalm's owl and red fox) and their alternative prey species (grouse and mountain hare). In grouse the change of numbers was correlated with that of recruitment. Autumn vole numbers peaked about a year before the other species and extensive forest damage occurred at winter peak densities of voles. These population fluctuations are consistent with a predator-prey model for their regulation. In short the model suggests that vole-food plant interactions trigger the cycle of voles, that voles generate the cycle of predators and that these in turn synchronize alternative prey populations to the others at vole declines.For voles, grouse and red fox the amplitude was higher in the first cycle compared to the second one whilst the opposite was true for the mountain hare. Although temperature and cone crops showed large interannual variations they still implied that herbivore food conditions were better during the former cycle. Hence, the reduction of the amplitude of the vole cycle may be explained by inter-cyclic differences in plant food conditions, implying food shortage (as indicated by bark-eating) at different population levels. The similar decrease of grouse and red fox populations may also be explained by deteriorated food conditions and/or for the fox by an outbreak of sarcoptic mange (Sarcoptes scabiae var. vulpes). The increased amplitude of the mountain hare cycle was part of a long-term rise in numbers after a tularemia epidemic in 1967. This is interpreted as a recovery, probably towards the generally higher pre-epidemic population level.     

Sarcoptic mange in raccoons in Michigan

Sarcoptic mange is a cause of pruritic skin disease in domestic dogs and a wide range of wildlife species. We describe sarcoptic mange in free-ranging raccoons (Procyon lotor). Three adult raccoons from upper Wayne County, Michigan (USA), were captured, killed, and submitted for diagnostic evaluation. The animals were intensely pruritic, and two had advanced alopecic and crusting lesions over their dorsum and hind limbs. Skin scrapings and skin biopsies revealed crusting and hyperkeratotic dermatitis with high numbers of Sarcoptes scabiei adults, larvae, nymphs, and eggs. These raccoons were not otherwise debilitated, with minimal internal parasites, good body condition, and no evidence of infectious bacterial or viral diseases. Because sarcoptic mange is highly contagious and affects many species, including humans, transiently, it is important that wildlife biologists and rehabilitators include sarcoptic mange in their differential list for raccoons exhibiting pruritus and alopecia.     

First description of sarcoptic mange in wild European rabbit (Oryctolagus cuniculus)

The European wild rabbit (Oryctolagus cuniculus) is a keystone species in the Iberian Mediterranean ecosystems being the staple prey of protected and endangered predators. Wild rabbits were once widespread, but the introduction of two viral diseases, myxomatosis in the 1950s and the rabbit hemorrhagic disease in 1989, resulted into a dramatic decline of its populations. Sarcoptic mange is a highly contagious parasitic infection caused by Sarcoptes scabiei. The first cases of sarcoptic mange in a wild rabbit population are recorded from a hunting area in Majorca (Balearic Islands, Spain). Five of 32 inspected rabbits (14.7%) were affected, with similar prevalences in summer and autumn. Sarcoptes scabiei were obtained from the edge of the lesions of two of the rabbits. The most frequently observed lesions were small areas of alopecia and crusts in the limbs. Affected limbs presented also a marked hypertrichosis and an apparent abnormal growth of the nails. One rabbit also presented lesions around mouth and nostrils. Parasitized rabbits were in significant lower body condition than healthy ones. According to previous reports of mange epizooties in other naïve wild species that caused marked short-term effects in their populations, this disease may pose a risk for the conservation of wild rabbit and their predators. Whether mange is endemic in rabbits from Majorca or it has been introduced is unknown. Game managers are encouraged to be aware of introducing sarcoptic mange during rabbit translocations.

     

An Invasive Vector of Zoonotic Disease Sustained by Anthropogenic Resources: The Raccoon Dog in Northern Europe

The raccoon dog (Nyctereutes procyonoides) is an introduced species in Europe with a continually expanding range. Since the species is capable of affecting local ecosystems and is a vector for a number of severe zoonotic diseases, it is important to understand its food habits. Raccoon dog diet was studied in Estonia by examining the contents of 223 stomach samples collected during the coldest period of the year, August to March, in 2010–2012. The most frequently consumed food categories were anthropogenic plants (e.g. cereals, fruits; FO = 56.1%) and carrion (e.g. carcasses of artiodactyls and carnivores; FO = 48.4%). Carrion was also the only food category that was consumed significantly more frequently by raccoon dogs exhibiting symptoms of sarcoptic mange than by uninfected animals. Small mammals, which represent intermediate hosts for the zoonotic tapeworm Echinococcus multilocularis, were more commonly recorded in samples also containing anthropogenic plants than expected by chance. Comparison of raccoon dog and red fox (Vulpes vulpes) diet in Estonia revealed higher overlap than found elsewhere in Europe, with ‘carrion’ and ‘anthropogenic plants’ making up the bulk of both species’ diet; however, raccoon dogs were more omnivorous than red foxes. Our results suggest that while the use of most food categories reflects the phenology of natural food sources, ‘anthropogenic plants’ and ‘carrion’ provide an essential resource for raccoon dogs during the coldest period of the year, with the latter resource especially important for individuals infected with sarcoptic mange. Since both of these food categories and small mammals are often found at supplementary feeding sites for wild boar (Sus scrofa), this game management practice may facilitate high densities of mesocarnivores and promote the spread of some severe zoonotic diseases, including alveolar echinococcosis, trichinellosis, rabies and sarcoptic mange.     

Strength of asymmetric competition between predators in food webs ruled by fluctuating prey: the case of foxes in tundra

In food webs heavily influenced by multi‐annual population fluctuations of key herbivores, predator species may differ in their functional and numerical responses as well as their competitive ability. Focusing on red and arctic fox in tundra with cyclic populations of rodents as key prey, we develop a model to predict how population dynamics of a dominant and versatile predator (red fox) impacted long‐term growth rate of a subdominant and less versatile predator (arctic fox). We compare three realistic scenarios of red fox performance: (1) a numerical response scenario where red fox acted as a resident rodent specialist exhibiting population cycles lagging one year after the rodent cycle, (2) an aggregative response scenario where red fox shifted between tundra and a nearby ecosystem (i.e. boreal forest) so as to track rodent peaks in tundra without delay, and (3) a constant subsidy scenario in which the red fox population was stabilized at the same mean density as in the other two scenarios. For all three scenarios it is assumed that the arctic fox responded numerically as a rodent specialist and that the mechanisms of competition is of a interference type for space, in which the arctic fox is excluded from the most resource rich patches in tundra. Arctic fox is impacted most by the constant subsidy scenario and least by the numerical response scenario. The differential effects of the scenarios stemmed from cyclic phase‐dependent sensitivity to competition mediated by changes in temporal mean and variance of available prey to the subdominant predator. A general implication from our result is that external resource subsidies (prey or habitats), monopolized by the dominant competitor, can significantly reduce the likelihood for co‐existence within the predator guild. In terms of conservation of vulnerable arctic fox populations this means that the likelihood of extinction increases with increasing amount of subsidies (e.g. carcasses of large herbivores or marine resources) in tundra and nearby forest areas, since it will act to both increase and stabilize populations of red fox.     

Morbidity and mortality of red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) admitted to the Wildlife Center of Virginia, 1993-2001

The medical records of 48 red foxes (Vulpes vulpes) and 35 gray foxes (Urocyon cinereoargenteus) examined at the Wildlife Center of Virginia (Waynesboro, Virginia, USA) from 1993 to 2001 were reviewed. The most common diagnosis in red foxes was orphaned (33%), followed by trauma (27%), undetermined diagnosis (23%), and sarcoptic mange (17%). Trauma (46%) was the most frequent cause of morbidity and mortality in gray foxes followed by orphaned (23%), undetermined (20%), toxoplasmosis (6%), presumptive canine distemper (3%), and rabies (3%). One gray fox had concurrent toxoplasmosis and presumptive canine distemper (3%). Similar diseases were detected in previous studies at a diagnostic laboratory; however in this study, trauma and orphaned animals were more common than infectious diseases. The lack of diagnostic information on some cases limited the usefulness of this study, and more emphasis should be placed on performing postmortem examinations of wildlife presented to wildlife rehabilitation centers.     

Population effects of sarcoptic mange in Barbary sheep (Ammotragus lervia) from Sierra Espuña Regional Park, Spain

The nonindigenous Barbary sheep population (Ammotragus lervia) of the Sierra Espuna Regional Park (Murcia, Spain) suffered an outbreak of sarcoptic mange between 1991 and 1995, which contributed to a population decrease of 86%. This study presents the results of two population surveys conducted in 1994 and 1999 based on the fixed point and itineraries method (FPI) and the excrement count (EC) method, as well as data from demographic estimates and clinical observations conducted by the Regional Administration of Murcia. Results of surveillance for mange are given between 1992 and 1995, because no animals were observed with sarcoptic mange in 1999. Prevalence of mange peaked in 1994 and then declined. During the regression phase of the epidemic, there was a higher infection rate in males (21.9%) than in females (16.6%) or young animals (5.1%). Males over 5 yr old were the worst affected age group, followed by subadults of both sexes. Few animals had generalized lesions of mange (7%), and most individuals (72%) had lesions of moderate severity. The most common locations of lesions were the neck, head, and back. The density of Barbary sheep in the Sierra Espuna Regional Park increased from introduction in 1972 until it peaked at 13 animals/km(2) in 1991, the year when the first case of sarcoptic mange was detected. After 2 yr of the mange epidemic, the average estimated density was 1.7 animals/km(2) in 1994, which increased to 5.0 animals/km(2) in 1999. The average group size also increased from 7.9 to 19.2 animals/group between 1994 and 1999. The sex ratio, expressed as the proportion of females in the total population observed, decreased from 0.61 in 1994 to 0.49 in 1999. The reproduction rate (kids per females per year) was essentially stable (0.59 in 1994 to 0.65 in 1999). Between 1994 and 1999 the population aged, with the number of young animals (<18 mo of age) decreasing from 45.3% to 36.6% from 1994 to 1999. In the same period, the proportion of males increased 21.4% to 32.6%. We believe sarcoptic mange acted as one of the regulating factors of population density after 1991 and that currently, although no sarcoptic mange lesions were observed in the 1999 survey, there is a demographic imbalance in sex ratio, age structure, and density.     

Synchronous and nonsynchronous population fluctuations of some predators and their prey in central Sweden

To test the alternative prey hypothesis (APH), we examined 29-yr time series of bank voles (indexed by snap-trapping) and 6 game species (indexed by bag records) from Gavleborg county, central Sweden, for the occurrence of synchronous population fluctuations Only voles and the 3 grouse species exhibited cyclic fluctuations, grouse fluctuations were highly synchronous, and positively correlated with vole fluctuations Although hares were positively correlated with grouse, they were negatively correlated with voles Fox were positively correlated with voles and grouse, however, a strong negative relationship was observed between fox and hares During a sharp decline in fox numbers during the early 1980's due to sarcoptic mange, both grouse and hares exhibited a strong positive numerical response, but, not in synchrony In addition, grouse exhibited large fluctuations during the fox decrease whereas hares did not Due to the contradictory predator-prey interactions observed, these results provide only partial support for APH     

Development of resistance to sarcoptic mange in ibex

Sarcoptic mange affects mammal host species worldwide and, particularly, wild Caprinae throughout much of Eurasia. In the Iberian Peninsula, several outbreaks of sarcoptic mange in Iberian ibex (Capra pyrenaica) have been reported since the 1980s. Using data from a period of long-term monitoring and a seasonal autoregressive integrated moving average (SARIMA)-generalized autoregressive conditional heteroscedasticity (GARCH) model approach, we performed a time-series analysis of the monthly prevalence of sarcoptic mange in the Iberian ibex population in Sierra Nevada Natural Space in southern Spain. In January 2003–March 2021, we documented a significant negative trend in sarcoptic mange prevalence, albeit with some interannual peaks. These findings can only be explained if a certain level of resistance to sarcoptic mange exists in hosts that, along with other factors, could provoke this reduced prevalence. Prevalence values varied seasonally, with maximum values in spring and minimum values at the end of summer, which may be due to factors linked to climate, host behavior, and endocrine activity. Our model predicts that the prevalence of sarcoptic mange in the Iberian ibex will continue to decrease over the next 2 years. Despite the inherent challenges involved, diagnosing and monitoring of wildlife diseases are integral to obtaining reliable epidemiological data and designing appropriate management strategies.     

Eradication of Porcine Sarcoptic Mange within a Health Declared Production Model

The success of a large-scale eradication programme against sarcoptic mange was evaluated in piglet producing herds belonging to the health class LSO 2000. These farms are monitored to be free from sarcoptic mange, swine enzootic pneumoniae, swine dysentery and progressive atrophic rhinitis. The local veterinarians were instructed to eradicate sarcoptic mange from the herds by 2 ivermectin injections 14 days apart or 3 treatments with phoxim pour-on 6 days apart before the farms were able to join the health class. The study consisted of a questionnaire administered to the farmers, farm visits and follow-ups associated with the regular control of the health class. A questionnaire was sent to all of the 379 accepted farrowing farms. Altogether 323 farmers had initiated an eradication programme at least 7 months before the questionnaire was distributed and 96% of them believed that the mange eradication programme had been successful. In most of the successful herds (90%), the local veterinarian had treated the animals by the recommended methods, and the majority of the farmers (88%) had cleaned and sprayed the pens with insecticides on the days of treatment. Three out of the 7 unsuccessful farms had employed methods other than those recommended. Twenty-five herds were randomly selected for an intensified control. The rubbing index was ≤0.1 in all herds visited, indicating freedom from mange. Sows or gilts, 15–20 animals per farm, were skin scraped and no Sarcoptes scabiei was found. The same animals were blood sampled and serum antibodies to S. scabiei were measured by an indirect ELISA. All except 1 farm had low optical density (OD) values in most of the samples. The owner of that farm had become uncertain about the mange status of the herd and had recently retreated all animals with acaricides. The number of complaints about mange in the finishing units buying health class feeder pigs was low. The study demonstrates that it is possible to run an eradication programme against sarcoptic mange, in which a large number of farmers together with their veterinarians participate. It is possible to eradicate mange not only at the herd but also at the population level. The ELISA test employed proved to be a possible tool to monitor the efficacy of mange-eradication programmes.     

Flexible spatial organization of urban foxes, Vulpes vulpes, before and during an outbreak of sarcoptic mange

The social and spatial organization of urban fox groups prior to and during an outbreak of sarcoptic mange was compared with predictions derived from the resource dispersion hypothesis (RDH). We investigated the availability of three key resources. Neither daytime rest sites nor breeding sites appeared to be limited in availability. The availability of food deliberately supplied by local householders was examined by questionnaire surveys. The daily and weekly amount of food supplied was greatly in excess of the minimum requirements of a pair of foxes, but was consistent between territories. The availability of this food source increased markedly as a result of more people feeding the foxes. In agreement with the RDH, group size prior to the outbreak of mange increased from 2.25 animals (N=4) to 6.57 animals (N=7). Before the outbreak of mange, two territories were divided. Increased scavenge availability on smaller territories may have promoted these changes. Excluding these spatial changes, territories were very stable between years. After the outbreak of mange, group size declined as a direct result of mange-induced mortality. Surviving animals increased their ranges only after neighbouring groups had died out. Ranges did not increase in size in response to a decline in food availability. Nor were the increases in range size associated with the relinquishment of parts of the existing territory. These postmange changes are contrary to the RDH. Three factors may have promoted these changes: the elimination of interstitial space, the forced dispersal of young or future division of the territory. Copyright 2000 The Association for the Study of Animal Behaviour.     

Studies of disease in the Red fox (Vulpes vulpes) in Northern Ireland

Some 720 foxes were examined for signs of disease and parasites, incidental to an intensive ecological study. The epifauna, skin infections, intestinal helminths and lesions of internal organs are described and rates of infection given. Important diseases included sarcoptic mange, which is a major debilitating factor and probably a fatal infection. Leptospirosis was common, antibodies were recorded in the blood, and chronic interstitial nephritis was a frequent condition of the kidneys. The nematodes Uncinaria stenocephala and Toxocara spp. were often present as parasites of the alimentary canal and may be a mortality factor in cubs. The cestodes and ectoparasites alone would appear to be of little importance and largely reflect the diet of the fox.     

Numerical responses by populations of red fox and mountain hare during an outbreak of sarcoptic mange

Summary During a severe outbreak of sarcoptic mange (Sarcoptes scabiei vulpes) starting among red foxes (Vulpes vulpes) in Sweden in the 1970s, we studied: 1) the establishment and spread of the disease in northernmost Sweden (by inquiries), and 2) the 1970–84 bag records for foxes and mountain hares (Lepus timidus) (an alternative prey to the fox's main prey, voles). Since the first case of sarcoptic mange in 1975 the disease spread rapidly, with >50% of the hunting organizations having reported the disease in 1981 and >75% in 1983. Also the disease became more abundant within the areas affected. In areas with a low mange infection rate (index) the number of foxes killed in the 1980s did not deviate markedly from the average level in the 1970s. However, there was a slight tendency towards a decline in areas with a medium index and numbers declined markedly where the index was high. Hare harvests initially were low (after a tularemia epidemic) in the 1970s. In that decade harvests increased dramatically and stabilized, increased gradually or changed little, respectively, where mange infection rates were low, medium or high in the early 1980s. In areas with a low mange index hare harvests remained cyclical and at the same level in the 1980s as in most of the 1970s. However, in areas with a medium index harvests increased and seemed to begin to lose their cyclicity, and where the index was high the low and relatively stable hare harvests increased annually. A predator-prey hypothesis, assuming predators to synchronize alternative prey declines to those of the cyclic main prey, predicts that a predator reduction would cause a gradual disappearance of the cyclicity and increasing numbers among alternative prey. Our hare data are partially consistent with this prediction.