Part 3 . Endemic TB In High Density Badger Populations ?

There have been a number of detailed studies of badger ecology in relation to epidemiological patterns of TB . Numbers with TB, and those infecTIOUS, as one-off excretors or multiple shedder superexcretors identified by :-

A.Clinical samples of cage trapped badgers , Tr Tracheal swab, F rectal faeces, U urine, swab from B Bite wounds, A abscess or swollen lymph nodes especially in throat (submandibulars);
B. Latrine faeces;
C. Blood samples with eg. Brocktest trials ;
D. autopsy of any badgers recovered , most = RTAs.

1. Woodchester Park in Glos., Sussex, Staffs., Thornbury in Avon, Steeple Leaze in Dorset, Cornwall (Kea and Feock farms, Cheeseman 1981; Zuckerman 1980, p. 73).
2 . Also, the Brocktest/Badger cull/ Perturbation studies :- North Nibley , Glos. (17 sq.km., Tuyttens 2000 a & b);
and the RBCT Triplet E Reactive TEE cull in Wilts ( 100 sq.km., DEFRA SE 3108, Macdonald 2006).
3 . Plus the badger VES 2 Vaccine Efficacy Study near Cirencester, Glos. ( 55 sq.km., Chambers 2011).

THREE sub-sections :
A. These studies in detail ; B. Few TB Brocks per social group ;
C. Few excretors & superexcretors, so within/ between clan spread ?

Two dogs that did not bark in the night !

Although these very detailed studies claim to prove TB is self-maintaining in high density badger populations, amongst several dozen papers, the most striking fact to emerge is how few infecTIOUS badgers were found; so very few clear cases where badger A gave TB to badger B; and hence despite supposedly " endemic" TB for decades, NO Proven cases noted where they actually Caused ANY cattle herd breakdowns ! In truth, the clear pattern is of cattle TB persisting in high density dairying areas, with spillover to incredibly small micropockets of a few badger clans at the epicentre of the TB herd/s incident; with little evidence of spread outwards to other clans, just as shown in the "clean ring" culls 1982-6 (Krebs 1997); and being only "pseudo-endemic" with little if any TB spread within these clans, so dying out after a few years with the "natural" death of these accidental victims ( boars with fulminating TB may die early ; Delahay 2000, Wilkinson 2000, 2009).

A. These studies in more detail : -

Woodchester

Summarising the data from dozens of papers, concerning the DEFRA /CSL-FERA Badger study area near Stroud in Glos. since 1975 ... there have been at least three clear TB episodes, as shown in Figure above :-

1. Beech tree sett

The first televised "Badger Watch" in 1977 unfortunately coincided with the first herd breakdown and discovery of TB badgers in the 11 sq.km. study area with 32 badger clans. 1977-9, 4 cattle reactors, 2 VL. So by 1980, amongst 14 badgers there had been just 7 with TB , 3 died of TB and 4 culled. Atypical behaviour included 1 badger in a barn, and 1 boar over 2 years visited 4 clans or social groups, but mostly using unoccupied setts ( Beech, Arthurs, West, Larch ). (MAFF reports 2-5, Cheeseman 1981). From 1981-5 an additional 2 clans affected , but only 12 TB badgers (Cheeseman 1981, 1988, Krebs 1997:- map p. 48). Seemingly, TB died out at Beech Tree in 1988, but reappeared in 1993 (Delahay 2000).

2. North Woodchester/Atcombe

2 herd contiguous breakdowns 1978/1979, so badger TB in 2 contiguous "micropockets" culled , but only 14 TB badgers out of 67 culled; from 6 of 11 clans (these were , 12 TB+ out of 38 in 4 out of 5 clans; and 2 TB+ out of 29 in 2 out of 6 clans . Adding 3 adjacent clans yielded 0 TB badgers, so just 14 TB + out of 85 culled, from 6 out of 14 clans..but at least 1 badger with TB missed by the cull may have deposited TB faeces in 2 further adjacent clans (1982 Nettle, 1984 Old Oak ). These culls are Glos. 1, 2, & 3 (Krebs 1997, p. 46). Recolonisation over 10 years re-established almost identical clan territories ; TB reappeared in 5 badgers but NOT found until presumably a further herd breakdown in 1988-9 (Cheeseman 1981, 1993).

3. Inner ring farms

Four contiguous farms 1987-9 had 93 reactors, so the whole Jacks Mirey clan caught TB . MAFF's tunnel vision and "idee fixe" assumed a badger source, and NO contiguous spread ! ; but the initially undetected breakdown probably started as early as 1984.. 1 latrine positive faeces (Krebs map p.48), so the TB badger in a barn November 1986, was a late victim, and CSL/MAFF were surprised to note that the cattle TB peaked before that in badgers ! ( Delahay 2000; Newell 1997; Wilesmith 1991).

4. Other breakdowns

Published papers do not record probable new breakdowns from c. 1990 onwards, starting TB in additional , particularly eastern clans eg. Wych Elm and Cedar in 2000-1 (Garnett 2005); and a number also occured just outside the study area boundary .. so marked "emigrant" TB badgers found outside (see Krebs map p. 48). It is remarkable that between 1981 - 1994, out of 868 known badgers there were just 128 with confirmed TB, 89 of which (70 %) were in the 6 core clans (Beech above), and only 41 infectious excretors, plus JUST 17 superinfectious badgers over 14 years in 11 sq.km. (Smith 1995). And between 1982 - 1991 TB was confined to western clans; 64 % in just 7 clans ( Arthurs, Septic Tank, West, Yew for 12 years, and from 1987 also in Jacks Mirey, Junction, and Larch for the next 9 years. No excretors in eastern clans until 1987, or superexcretors until 1996 ( in Nettle, Old Oak; Delahay 2000). Hard to believe this was truly self-maintaining , without additional sporadic top up from cattle (although "officially" this was not supposed to be happening !!).

NOT SELF-SUSTAINING .. despite the dozens of papers, little hard evidence of spread within or between clans, and TB nearly died out in the study area overall 1984 & 1993.

Delahay 2000 (Figure 1); Shirley 2003 shows that for 1982-96, in the 22 core clans in 7 sq.km. , none had TB throughout the 15 years, they had up to 2-5 separate "episodes" with TB; so : -- 0 clans had TB all 15 years; 1 clan had TB for 14 years ; 1 for 13 y; 3 for 12 y; 0 for 11 y; 5 for 10 y; 1 for 9 y; 0 for 8 y; 2 for 7 y; 1 each for 6, 5, 4, 3 y; 2 for 2y; 1 for 1 y; and 2 never had TB.

Selected References : - Benham 1993; Brown 1993; Chambers 2002, 2011; Cheeseman 1981 a & b, 1985, 1988 a & b , 1989, 1993; Clifton-Hadley 1991, 1993; Courtenay 2006; Delahay 2000; Garnett 2002, 2003, 2005; Hayden 1993; Krebs 1997; Newell 1997; Nolan 1994; Rogers 1997 a & b , 1998, 1999, 2003; Ward 2010; Wilesmith 1991. AND ; Computer Simulation Models based mainly on Woodchester data :- Smith 1995, 2001 a & b ; Shirley 2003; Swinton 1997; Vicente 2007; White 1993, 1995 a & b ; Wilkinson 2000, 2004, 2009.

Sussex

1981-4. 3 contiguous herds, 19 reactors.. peak in 1982 when latrine faeces positive from all 8 study area clans . The 1984 cull found only 10 TB + badgers out of 47 culled, from only 4 clans (cull disrupted by protestors however). There were 1972-96 just 68 TB badgers from 1319 sampled (RTAs +culls) for the whole county; with the same unique Irish DNA Spoligotype as the cattle, probably going back to 1970s imports (Wilesmith 1983, Krebs 1997 ). The study revealed only a tiny number of TB badgers , apart from the cull ones, so clearly there was no widespread reservoir of TB in either badgers or cattle, so unsurprisingly NO TB found in other wildlife sampled (Wilesmith & Pritchard 1986). Steeple Leaze, by contrast, being a cluster of chronic herds with active TB spread resulted in TB in a few foxes, sika deer, and rats ( see below, Little 1982).

Staffordshire

Particularly interesting, since it was the last non-southwest county to go clear under Area Eradication , the parishes of Ipstones, Bradnop, Cheddleton . 10 problem farms (8 dairy), and farms F G H 1980-4 had 36 reactors, 23 VL , later on farm B went down with TB too. Initially, farm G covering the study clans yielded 8 TB badgers out of 45 culled , from 3 of the 5 clans. Extending the area found JUST 16 TB + altogether out of 145 culled (1-2 found dead).. including a few linked to farm B. From 1972-96 there were only an additional 10 RTA badgers, so just 26 TB + out of 604 sampled , so no widespread self-sustaining reservoir of badger TB even just after cattle TB eradicated in the county . (Cheeseman 1985, Hewson 1987 , MAFF 20).

Avon / Dorset / Cornwall studies (Cheeseman 1981).

Badger sampling did give some indication of a very few TB+ badgers associated with cattle hotspots : - Thornbury, Avon, 8 TB badgers out of 40 culled, and 31 TB + among 223 sampled (Cheeseman 1981; Gallagher 2000; Clifton-Hadley 1995); and Steeple Leaze, Dorset 15 TB+ out of 80 culled (Gallagher 2000; Little 1982 ; Wilesmith 1982); Cornwall 10 TB + out of 29 culled (Cheeseman 1981; Zuckerman 1980, p. 73 ). SO, just 64 TB+ out of 372 culled .....BUT , then badgers gassed pointlessly, so numbers culled unknown . However MAFF Reports give 1972-96 numbers ; just 451 TB+ / 3104 sampled Avon; 136 TB+ / 2126 in Dorset; 1118 TB + / 9036 in Cornwall...hardly major county-wide badger TB reservoirs.

B. Mostly just 1-2 TB badgers per clan or social group.. so hardly self-sustaining ?

North Woodchester

1978-9 , just 1 TB + in 2 clans; 2 TB + in 2 clans; 3 in 1 ; 5 in 1 ..so 14 TB+ /67 , from 6 out of 11 clans (Cheeseman 1993)

North nibley

1995-2000, 1 TB+ in 4 clans ; 2 in 8; 3 in 2 .. so 26 TB badgers, from 14 of 24 clans (Tuyttens 2000 a, b; Macdonald 2006 )

STAFFS.

1982, 1 TB + in 1 clan ; 2 in 1 ; 5 in 1 .. so 8 TB + /54 from 3 out of 5 clans (Cheeseman 1985)

Sussex

1982, 1 TB + in 2 clans; 3 in 1; 5 in 1 ... so 10 TB+ / 47 from 4 out of 8 clans (Wilesmith 1996)

Avon

(Thornbury) , 1979 , 1 TB + in 2 clans; 6 in 1 clan ... so 8 TB+/ 40, from 3 out of 7 clans (Cheeseman 1981)

Cornwall

1978, 2 TB+ in 1 clan ; 8 in 1 clan, .. so 10 TB+ /29 , 2 out of 6 clans (Cheeseman 1981)

TOTALS

1-2 TB badgers in 23 clans ; 3-8 in 9 clans = 32 TB + clans out of 61 culled ... amounting to JUST 76 TB+ badgers out of 263 culled. NB. adult badger density NOT reflected in TB prevalence ..lowest density Cornwall 4.7 ad/ sq.km. had highest spillover from cattle 34.5 % TB+.. whereas Glos. 1, 2, & 3 next door areas ..with 19.7 ad/sq.km. ranged in prevalence from 0 to 6.9 to 31.6 % (Cheeseman 1981, Krebs p.46)

RBCT 1998-2005, averaged 1.7 TB badgers/clan in 168 clans (see Table in culls work Section 4 below).

Four areas culling trial, ireland, 1997-2002, 1 TB+ badger in 205 setts, 2 in 67 setts, 3-6 in 25 setts = 431 TB+ /2360 culled , 960 sq.km. (SEE Part 4 culls; NB. includes buffer area culls, and "sett" = main +subsidiary so not equivalent to clans in above numbers ; Costello 2006).

In conclusion ,in England, there were only 1 or 2 TB badgers / clans in 23 out of 32 clans in the detailed studies above; as well as amongst 168 RBCT culls (Woodroffe 2009).; hardly suggesting a self-maintaining reservoir. But a realistic outcome from badgers seeking beetles and worms under the few TB point source cow pats , from the 1-2 VL /Visible Lesion reactors in most minor cattle herd breakdowns.

C. Badger infectivity :- excretors and superexcretors / within and between clan spread ??

The "first" wild TB badger/s were discovered in 1971 near Woodchester Park in Glos., with 2 in Glamorgan (Muirhead 1974; Evans 1981; Little 1982) . Soon afterwards it became "accepted wisdom" that high density badger populations constituted an endemic reservoir of TB, self-sustaining spread being 18 % via territorial bite wounding between clans, and 82 % respiratory spread within clans , with a significant sow to cub vertical (lactation) and "pseudo-vertical" aerosol close contact transmission component (Cheeseman 1988, 1989).

Alas this plausible but simplistic scenario simply does not stand up to scrutiny, as described above (SEE Badgers Part 1. Transmission/ Badger Infectivity ). Badger TB is a "Scrofula" caught by ingestion , beetles under cow pats, and there are too few VL Visibly Lesioned lung cases with infectious "sputum", so that little respiratory spread occurs even among communal "sleeping huddles" in underground nests; nor truly by bite wounding, which acquire secondary "septicaemia" infection in the sett environment (Corner 2012; Courtenay 2006; Gallagher 1979, 2000; Smith 2001). Mammary lesions are extremely rare so ditto to lactation direct to cubs (O'Boyle 1991- 2005).

However , computer models based largely on this early Woodchester data from 1975 onwards , duly concluded that with given threshold clan sizes / badger density / population dynamics and demography, and Guestimated within / between clan transmission rates TB prevalence in the population could be self-sustaining with observed prevalence of c. 10 - 18 % (Smith 2001; Delahay 2000; Vicente 2007). Unfortunately "Models are constructions of knowledge and caricatures of reality ", Beissinger & Westphal 1998 (Shirley 2003 ) :- and the KEY Assumption underpinning models and interpretation of Woodchester data ... IS that transmission is one-way, badger to badger to cow , AND NO Longer with any cattle to badger spillover element; BUT this is spectacularly WRONG ! The severity of the preceeding cattle herd breakdowns is :-

A. simply reflected by spillover to the ensuing prevalence in badgers.. the highest density badgers having the lowest TB prevalence as noted above (Krebs 1997, p. 46). And a FMD doubling of cattle TB doubling the prevalence in RBCT badgers including "unperturbed" RTAs (ISG 2007, p. 73-8, 84, 243 ).

B. hence also the apparent high numbers of cubs with TB in some clans after bad herd breakdowns ; not evidence of pseudo-vertical sow to cub transmission (Cheeseman 1981; Gallagher 2000; Newell 1997).

C. the first sign of bad herd breakdowns in "clear" areas is often finding dead or moribund badgers, often behaving atypically eg. using outlier setts and visiting barns ; as initially in Glos., including the Beech Tree and Jacks Mirey clans above (Muirhead 1974; Cheeseman 1981; Garnett 2005; Cresswell 1989). Terminally sick badgers and local die out heralded the start of the Gelli Aur university herd outbreak a decade ago, and perpetuated by a single anergic/ non-reactor cow recently found to be "riddled" with TB (Farmers Guardian reports). It seems that superexcretor badgers with emaciation and fulminating fatal TB, particularly boars, are often such High dose spillover victims (Gallagher 1979, 2000; Wilkinson 2000, 2009).

In truth, remarkably few TB badgers are found AFTER cattle breakdowns; and even in these study populations with supposedly self-maintaining TB , there are incredibly few excretor / superexcretors which Might be risk to other badgers or cattle... Part 1. Transmission / Infectivity, notes incredibly few with kidney TB and infectious urine. That is why models such as Smith 2001 and Shirley 2003 frankly admit a major lack of basic data on transmission routes or rates as regards : - within / between clan spread, progression from latent/ infected to excretor to superexcretor, or indeed often SELF-HEALING ... badgers seem to be more resistant to TB than originally thought :-
A. 5 cases (Gallagher 2000), ....and
B. 1 of the 21 badgers in the yard experiment had swollen lymph nodes but otherwise was "not infected" (Little 1982)....
C. and including from excretor back to non-infectious status, and
D. transient blood ELISA /Brocktest TB seropositivity ( Newell 1997; Chambers 2002, 2011) ; and
E. perhaps badgers shedding " ingested ?" bacilli in faeces or urine without becoming infected ( Sussex and Staffs. studies), "challenged" but not infected, as in the Brocktest studies in D (Smith 1995) or experimentally (Pritchard 1987)
F. ingestion entry site via submandibular lymph nodes often heal, so obscuring initial transmission route (Cheeseman 1985);
G. lung tubercles may become encapsulated or "closed" (Gallagher 1998).

These clinical sampling studies show that bacterial shedding is intermittent, and some 42 % of excretors revert back to non-excretor status (Delahay 2000; Wilesmith 1991). Between 1985-1998 (14 years), in the 5 worst affected clans among 128 blood test or culture positive badgers, 37 of 61 were excretors only once (Chambers 2002). Hence clinical sampling may only detect 20 to 28 % infectious badgers amongst those actually with TB ( Pritchard 1986, 1987; Chambers 2002). NB. Experimental studies showed as few as 10 cfu inoculated endo-bronchially may infect badgers (Lesellier 2010); BUT both Chris Cheeseman and Des Delahay remarked that even with a sputum positive "hoocher" in a cla, and sleeping huddles of 5-6 badgers in underground nest, still ONLY 1-2 TB badgers / social group .. the wrong kind of aerosol droplets ? / sick badgers may choose to live apart from the main group (see boar in Beech Tree sett above)/ AND , as noted by Gallagher 1998, seemingly lung lesions may "self-heal" and become encapsulated as in human TB, so no shedding of bacilli (UNlike cows, where lung lesions remain "Open" throughout (Francis 1947, 1958).

Sorry, seems to me some "Scientific" badger TB models conform amusingly to the GIGO Principle :- Garbage in = Garbage Out.. using such wild Guestimates as badgers cause 60 or 96 % of cattle breakdowns, and 1 superexcretor infects up to 5 cows per year (more than an active spreader cow !), then despite mythical cyclicity and "perturbation" effects , badger culls, including 41 % accurate live Brocktest ones/ vaccines / or fertility control assuming mass action Stochastic density dependence, Might work over a 50 - 100 year Simulation !! Wonderfully insane solutions to a non-existent problem , or as a vet said way back "Political expediency pursued way beyond the point of absurdity " (Coffey 1977).

It is generally accepted that only superexcretors are likely to be truly a risk to other badgers or cattle, with clinical shedding of bacilli at several recaptures or in multiple samples / badger , mainly : - Tr = Tracheal aspirate, F = faeces (swallowed coughed up lung exudate), U = Urine , B = Bite wound , A = Abscess, particularly submandibular lymph nodes in throat indicating ingestion Scrofula. BUT remarkably few excretors or superexcretors each year amongst 22 core Woodchester clans in 7 sq.km. :- over 15 years 1982-96, only 1-7 excretors / a, OR JUST 1-5 superexcretors /a ( Delahay 2000; Cheeseman 1989; Vicente 2007 ). And in the RBCT cull sample : ONLY 166 OUT OF 9919 DETAILED BADGER AUTOPSIES (ISG 2007, p. 77).

Detailed data From several these studies show incredibly few infectious badgers : -

Woodchester

1981 - 1994 (14 yrs), 868 badgers, but only 128 infected, just 41 excretors and 17 superinfectious (Smith 1995). 1981 - 1994, re-classifying this data, 25 now called superexcretors, 12 boars (10 B, 7 Tr), 13 sows ( 3 B, 12 Tr)(Smith 2001). 1981 - 1990, 49 excretors, 18 (37 % ) Urine positive ; but in 1990 12 clinical cases 5 Tr, 7 F, U 2, B 6 (Wilesmith 1991).... these included some from worst clan Jacks Mirey, but Newell 1997 found 11 clinical excretors; Brown 1993 between 1988-90 found out of 13 badgers, 6 had TB : - 2 Tr, 3 F, 2 U, 1 B, and only 2 superexcretors. 1975 - 1993 (17 yrs ) records for 4358 individual badgers, 307 recovered for autopsy of which just 47 TB + , 19 died of TB , showing lesions in .. 20 head lymph nodes l.n.s; 40 lung ; 20 broncho-mediastinal l.n.s; 8mesenterics; 19 kidney ... and out of 25 with good serial recapture clinical records 11 with TB comprised 7 Tr, 7 F, 4 U , 5 B (Clifton-Hadley 1993). 1981 - 1985, only 12 TB badgers in 6 clans in study area, clinically 4 Tr, 3 F, 2 U, 1 B, 7 A. Unsurprisingly, sampling latrine faeces 1983-7 found just 32 TB + out of 4023 , with 7 in 11 from 1 sick badger (Cheeseman 1988).

Given this paucity of infectious badgers amidst the dozens of papers on the "endemic TB" Woodchester population, there was little evidence of spread within social groups; nor clan to clan spread : - 1981 - 1994, only 13 bite wounds amongst just 25 superexcretors (Smith 2001), and 1978 - 1995 (18 yrs), among 1763 badgers, 475 with reliable movement records , only 7 out of 29 superexcretors moved to the neighbouring clan (Rogers 1998).

Sussex , 10 TB badgers among 47 culled from 4 of 8 clans; clinical sampling found 2 excretors : 1 Tr, 2 F, 0 U; and whilst positive latrine faeces occurred in all 8 clans at the cattle peak 1982, only 27 scats TB + from 1064 (Pritchard 1986).

Staffordshire, 8 TB + out of 45 culled , but only 1 F clinical sample; and probably all 13 TB + scats out of 541 latrine samples were from 1 terminally sick badger (Cheeseman 1985, Hewson 1987).

Gloucestershire

A. Cirencester , the 3 year VES 2 Vaccine study found 844 badgers in 55 sq.km. Among 262 from 64 clans caught more than once there were ONLY 18- 33 TB + based on blood tests and/ or culture for M. bovis . And 4854 clinical samples yielded just 189 positive : - Tr 71, F 28 , U 41 , B 40 , Other 9. With such a low level of badgers with TB , and even lower infectIVITY, Very hard to see how TB might be self-maintaining within this "population" (Chambers 2011).

B. North Nibley , 17 sq.km. .. amongst some 29 badgers culled only 5 clinical excretors, and 2 badgers moved between neighbouring clans (Tuyttens 2000 a & b, Macdonald 2006).

Wiltshire

RBCT Reactive Triplet E, only 23 TB + out of 188 culled ; clinical sampling found Tr 16, F 2, U 14, Pus (wound ) 6; and only 14 dispersals over 4 years (DEFRA Report SE 3108, ISG 2007).

In conclusion . These "Textbook " high density badger populations supposedly had endemic TB ; BUT they had Very few TB badgers, and FAR TOO FEW Superexcretors to : --
A. maintain "pseudo-endemic" TB by within / between clan spread, without further top-up from cattle ; NOR
B. in some 35 years , to have demonstably Actually Caused ANY cattle herd breakdown/s whatsoever !!