Paratuberculosis in Wild and Farmed Deer

14.1.1 Wild and captive deer

There have been a few isolated reports of para­tuberculosis in deer prior to 19 70, but since then it has been reported frequently in a range of deer species in the wild and in parks, zoos and enclosures in a number of countries (Temple et al., 1979; Pacetti et al., 1994).

(Sharp et al., 199 7; Simpson et al., 2012). A serological survey of free-ranging cervids in Norway (Tryland et al., 2004) showed evidence of paratuberculosis in moose (Alces alces), red deer, roe deer and semi-domesticated reindeer, but no evidence was seen in wild reindeer. Paratuberculosis has been diagnosed in wild red deer (Cervus elaphus) in Germany (Fritsch et al., 2012), where it is suspected that disease may have been transmitted from domestic cattle to wild deer.

14.1.2 Farmed deer

Since the early 1980s, paratuberculosis has been diagnosed on deer farms in Europe, Asia, North and South America and Oceania. Reported cases include farmed deer in the UK (Gilmour, 1988; Fawcett et al., 1995), Ireland (Power et al., 1993), Denmark (Jorgensen and Jorgensen, 1987), Germany (Commichau, 1982), Belgium (Godfroid et al., 2000), New Zealand (Gumbrell, 1986; de Lisle et al., 1993), Canada (Starke, 1991), Hungary (Pavlik et al., 1994; Machackova et al., 2004), the USA (Manning et al., 1998), Argentina (Mereb et al.,

‘Corresponding author: rory@drl.net.nz

© CAB International 2020.

(eds M.A. Behr et al.)

1994) and Australia (Kennedy and Allworth, 2000).

New Zealand is unique in that it has a population of approximately 1 million farmed European red deer (Cervus elaphus) and a smaller herd of North American elk (Cervus elaphus nel- soni/manitobensis), a farming practice not com­monly employed internationally. The first case of paratuberculosis in farmed red deer in New Zealand was diagnosed in 19 79 (Gumbrell, 1986) and paratuberculosis has been the sub­ject of investigation and research since the mid-1990s. Passive surveillance, principally by the examination of suspect tuberculous le­sions identified in deer slaughter plants, subse­quently resulted in Mycobacterium avium subsp. paratuberculosis (MAP) being identified in over 600 farmed deer on 300 properties (de Lisle et al., 2003). The study suggested that the herd prevalence at that time was approximately 6%. Serological surveillance for paratuberculosis on 62 7 of New Zealand's deer farms has been carried out since 2000, using blood samples submitted as part of the national tuberculosis eradication scheme (Griffin et al., 2003, 2005). The findings from this project suggested a na­tional prevalence of herd infection of around 63% (Griffin et al., 2006). A recent non-random sample of 115 New Zealand deer herds of un­known infection status found that 43% had pooled faecal samples culture-positive for MAP (Glossop et al., 2006). Since 2007 abattoir sur­veillance and recording of enlarged mesenteric lymph nodes suggestive of paratuberculosis has been in place in New Zealand involving >95% of deer farms. While low prevalence outbreaks of clinical paratuberculosis occurred commonly prior to 2010, regular herd testing with ELISA and culling of reactors since then has reduced clinical outbreaks of paratuberculosis in New Zealand deer herds to a very low level.

14.1.3 Disease

The pathogenesis of MAP infection in cervids is different from that observed in other ruminant species.

14.1.5 Epidemiology

Although MAP strains of both MAP-C (Cattle­type or Type C) and MAP-S (Sheep-type or Type S) have been isolated from deer, MAP-C appears to be both more common and more pathogenic and is responsible for the outbreaks of serious disease in both young, farmed red deer (O’Brien et al., 2006; Verdugo et al., 2014) and in wild red deer (Galiero et al., 2018). A more detailed discussion of the different strain types of MAP is given elsewhere (see Chapter 6, this volume). Clinical disease developed in 5 out of 16 deer, 21-38 weeks after heavy oral experimental challenge of 4-month-old deer with a MAP-C strain, while the MAP-S strain was relatively non-pathogenic (Mackintosh et al., 2007). Over 95% of isolates of MAP from farmed deer in New Zealand have been MAP-C (de Lisle et al., 2006).

Young deer appear to be more susceptible to clinical disease than older animals.

Intrauterine transmission from dam to fe­tus has been reported in red deer. van Kooten et al. (2006) reported that in a sample of 9 late-stage pregnant hinds clinically affected by paratuberculosis, 9 out of 10 (90%) of their fe­tuses were BACTEC culture-positive for MAP. In another study, MAP was isolated from 78% of fetuses of a group of 18 subclinically infect­ed red deer hinds (Thompson et al., 2007). In contrast, MAP was isolated from only 39% of fetuses from clinically affected dairy cows and 9% of fetuses from subclinically infected dairy cows (Whittington and Windsor, 2007). In sheep, intrauterine transmission is thought to occur in as well as culling infected hinds, because their calves will almost invariably be infected either in utero or shortly after birth.

In addition, a number of vaccines have been used for decades, including in deer, where they provide partial protection by reducing faecal shedding (Harris and Barletta, 2001). In Scotland, vaccination was used in deer on a farm that experienced a severe outbreak of paratuberculosis; although infection still oc­curred, there was a marked reduction in the incidence of clinical disease (Fawcett et al., 1995). There have been a small number of efficacy studies in deer of various live attenu­ated and killed MAP vaccines (Mackintosh et al., 2003, 2005, 2008), which showed that oil-adjuvanted killed vaccines gave some pro­tection against clinical disease but did not pre­vent infection. However, vaccination produced some interference with TB diagnosis, resulting in false-positive reactions to the bovine tuber­culin skin test. Because of this interference, it is recommended that these vaccines are not used in breeding animals on deer farms in New Zealand; they may be cost-effective in young deer raised for slaughter as meat animals, as these animals would not need to be tested for TB. Vaccination with a killed MAP strain 316F vaccine (Silirum) in a randomized clinical trial in young deer in naturally exposed herds sig­nificantly reduced paratuberculosis incidence by 60% by approximately 12 months of age, but did not reduce the proportion shedding (Stringer et al., 2013b).

14.2