Risk factor

Disease association

Biological basis

Foot hygiene

Increased muddiness of environment associated with an increased risk of BDD. (Rodríguez-Lainz et al., 1996, Rodríguez-Lainz et al., 1996)

Skin barrier weakened by continuous exposure to moisture and increased risk of damage. Abrasion of skin was required to transmit BDD in experimental conditions (Read, Walker, 1996, Gomez et al., 2012). Also, the presence of digital dermatitis treponemes in the bovine GI tract suggests these organisms may be shed into faeces (Evans et al., 2012). Footbaths may decrease the risk of BDD by improving foot hygiene and reducing exposure of the feet to slurry.

Increased animal hygiene associated with a reduced risk of DD (Hultgren and Bergsten, 2001)

Footbathing reduces the risk of DD compared to farms that do not footbath (Rodríguez-Lainz et al, 1996), Rodríguez-Lainz et al., 1996)

Claw trimming

Lack of washing hoof trimming equipment between cows increased the risk of DD (Wells et al., 1999)

BDD is considered to be highly contagious and thought to be transmitted through hoof trimming equipment (Wells et al., 1999). BDD treponemes are frequently identified on claw trimming equipment (Sullivan et al., 2014).

In addition, claw trimming is considered important for ruminant foot health since it reduces mechanical pressures (Raven, 1985).

Use of a primary hoof trimmer who trimmed cows' hooves on other operations increases the risk of DD (Wells et al., 1999)

Regular claw trimming twice a year reduces the risk of DD compared with longer durations between trimming (>7 months) (Somers et al., 2005)

Housing and land access

Cows kept on pasture have a decreased risk of DD than cows housed indoors (Blowey and Sharp, 1988; and Rodríguez-Lainz et al, 1996, Onyiro et al, 2008)

These factors influence the exposure of cows to poor hygiene and moist foot conditions, which lead to risk factors associated with poor foot hygiene.  

Cows with daily access to pasture in winter have a decreased risk of DD compared to those animals which do not (Wells et al., 1999)

Heifer replacement

Buying in new heifers increases the risk of BDD (Rodríguez-Lainz et al, 1996, Rodríguez-Lainz et al, 1996, Wells et al, 1999)

Since BDD is considered to be a contagious infectious disease, it can be introduced with infected heifers (Read and Walker, 1998).  Asymptomatic animals harbouring BDD treponemes in rectal tissues may these organisms and therefore transmit infection (Evans et al., 2012). Finally, seemingly healed lesions may reactivate and cause subsequent spread (Berry et al, 2010, Berry et al, 2012).

Flooring type and cleaning.

Grooved concrete > Smooth/slatted concrete > Textured concrete for increased risk of BDD (Wells et al., 1999)

The abrasiveness or slipperiness of concrete (Wells et al., 1999) may increase the risk of BDD by leading to micro-abrasions of the foot. In addition, improved environmental hygiene with the use of rubber slatted flooring (Hultgren & Bergsten, 2001) or regular removal of manure reduces exposure to moist conditions (Somers et al., 2005).

Increased risk of BDD from solid floor compared to use of rubber-slatted flooring (Hultgren & Bergsten, 2001)

Increased risk of BDD from solid floor compared to use of slatted flooring with scraper system (Somers et al., 2005)

Nutrition

Cows receiving maximum concentrate supplement 2 weeks after calving are at increased risk of BDD compared to those receiving their maximum concentrate supplement at 3 weeks (Somers et al., 2005)

Excessive concentrate shortly after calving may enhance the postnatal metabolic imbalance. Higher metabolic stress increases susceptibility to diseases and therefore BDD (Enevoldsen et al., 1994). Moreover, by-products are typically protein-rich and may cause an inappropriate diet with excessive protein intake identified as a potential risk factor for BDD previously (Somers et al., 2005). Finally, inappropriate body condition score may lead to an increased susceptibility to infectious diseases via suboptimal immunity (Schopke et al., 2013)

Feeding of by-products (Somers et al., 2005)

Animals with a body condition score too high or low have a higher risk of developing DD (Schopke et al., 2013)

First parity cows have increased risk of DD (Read & Walker, 1998b, Rodriguez-Lainz et al, 1999, Somers et al., 2005)

Primiparous cows exposed to severe changes in nutrition and environment in the period either side of calving (Somers et al., 2005) and this is thought to lead to suboptimal immunity (Blowey et al., 1994, Read & Walker, 1998)

Increased risk of DD during lactation than dry period (Read & Walker, 1998, Murray et al, 2002, Somers et al., 2005)

Lactating cows frequently shed more liquid faeces due to diet, whereas dry cows excrete solid faeces, since they are fed a higher proportion of roughage. Liquid faeces are associated with more unhygienic and moist floor conditions (Somers et al., 2005)