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This article was published in 1987
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Ovine Johne's Disease (Paratuberculosis) in Carcoar P.P.D. (1980-1987)

C.H.R. DENT, B.V.Sc., M.V.Sc., Dip. A.H., M.A.C.V.Sc., M.R.C.V.S., Veterinary Inspector, CARCOAR

INTRODUCTION:

In November, 1979, a wasted 5 y.o. Dorset ewe with 2 w.o. lamb at foot was sacrificed on a property near Blayney: the owner reported the deaths of several ewes in previous months which had also shown progressive weight loss but good appetites, no fever or other outward signs of illness except diarrhoea in one or two.

A field diagnosis of chronic Nephritis was not confirmed by histopathology done at Glenfield V.R.S. Keith Walker, examining pathologist, 'took up' a query on the Specimen Advice Note—'(? Johne's Disease)'—and commented upon it. So began my association with this disease, and its increasingly frequent recognition both in the field and the laboratory, both at V.R.S. and R.V.L. Orange, in the subsequent years.

I should say that I did not recognise the initial case as being one of Johne's Disease (J's. D.), never having seen it before either in sheep, cattle or goats: certainly p.m. examination had eliminated some other causes of wasting, (viz. abcesses, neoplasia, mineral deficiencies, Fasciola, dental disease, chronic infections), but later investigations on the property soon confirmed the presence of Johne's Disease—both John Seaman (V.R.O. at Glenfield, and at R.V.L. Orange since 1982) and Ian Gardner (V.O. Orange, (now S.V.O. (pigs))) assisted in this work.

OCCURRENCE:

To date ovine J's. D. has been confirmed (history, histopath, bacto.) in twelve flocks in Carcoar P.P.D.—the latest diagnosis was only made in February, 1987.

The infected flocks lie near Blayney, but to its south and south east—(I doubt that this is merely by chance, but reckon it is really just the result of a gradual unfolding of its perhaps long-time existence in District flocks).

I have not yet (in 20 years) encountered J's. D. in cattle or goats in the District: that is not to say that it has not been considered in differential diagnosis on odd occasions, but neither 'lab. proof' nor 'lab. suspicion' has yet been encountered.

The District has been used for livestock raising since its European settlement in the 1830's, and sheep and cattle have been raised in close association for many of these years. Goats (Angoras, cashmere) are more recent introductions, particularly in the last decade: they often run in association with sheep, or at least on the ground over which sheep have run previously.

If there is any possibility of cross-species transference on the infected properties, it doesn't appear to have happened yet.

To my knowledge J's. D. has not been recognised elsewhere in the N.S.W. sheep-flock—it seems to have been strongly suspected (if not proven) in 1 ex 6 sheep running on Bairnsdale R.V.L. (McCausland, A.V.J. (1980) 56 (11): 564), but otherwise apparently has not been recognised in flocks elsewhere in Australia—even those running close to 'J's. D. +ve' cattle-herds or goat-herds in Victoria, or elsewhere!!

The initial cases encountered in Carcoar P.P.D. were confirmed by pathology, histopathology and bacteriology, and this lead to its reporting (Seaman, Gardner, Dent (A.V.J. (1981) 57 (2): 102) as having now been encountered in commercial sheep flocks.

J's. D. has been recognised in Australian cattle since 1925 and in goats since 1977: the focus of infection for our sheep cases has not been found—their appearance was related to the 'big-drought' (1980—1983), but I suspect J's. D. has existed for some (if not, many) years before its 'discovery'—maybe the stress of drought allowed it to become recognised.

CARCOAR P.P. DISTRICT:

This P.P.D. lies in the Central West of the State, being adjacent to Moss Vale, Bathurst, Molong, Forbes, Young, Yass and Goulburn P.P.D's.—most of which also have significant sheep, cattle and even goat populations.

It is approximately 0.7 m (607,017+) hectares in area, and (at 31 December 1986) has 1640 ratepayers.

It has three recognisable 'climatic zones', based on elevations above sea level and more roughly on the depths of snow in winter.

Zone 1:	'Racecourse Country'
('B' Division)	COWRA/CANOWINDRA	NO SNOW/HOT SUMMER EARLY SPRING BREAK (July)
	300-400 m. A.S.L.
Zone 2:	'Tableland Country'
('A','C' & pt. 'D' Divisions)	Central Tablelands	LIGHT SNOW / MODERATE SUMMER, SPRING (6 w. later)
	400-1000 m. A.S.L.
Zone 3:	'Mountain Country'
(pt. 'D' Division)	(OBERON), Black Springs	HEAVY SNOW/MODERATE SUMMER, SPRING (8 w. later)
	1000 m. A.S.L.

Features:

Most farms only have 300-400 ha. blocks, but there are some much bigger ones (4000 ha.) and some smaller.

In Zone 1:

Intensive agriculture (cereals, oil-seeds, lucerne) and horticulture (vegetables for canning), are found in association with fairly heavily stock properties: beef-cattle, fat-lamb raising are prevalent, and pig-raising is not uncommon (be it extensive or intensive )—only 2 dairies are in this area, but there are several significant horse studs (both Standardbred and Thoroughbreds).

In Zone 2:

There are reasonably large expanses of virgin eucalypt forest in the several deep river valleys in this zone. Agriculture is much less intensive here, as is horticulture (except for stone- and berry-fruit growing near Orange, and potato-growing nearer Blayney: most farms have small areas of cereal-crops grown for home-use winter-grazing and later grain-harvest.

Grazing (sheep, beef cattle and goats) are most frequent in this area, based on improved pastures of Phalaris, Ryegrass, Cocksfoot, and Sub-Clovers: there are 3 dairies in this area.

Sheep are mostly 1st Xbds ewes and British Breed rams (Dorset in the majority), for fat-lamb production. There are pure Merino flocks scattered throughout, as well as Merino-types (Zeniths, Polworths, Corriedales): the pure Merinos are particularly in the southern parts around Crookwell (super-superfine Merinos: 15.5 microns, 78% yield and 28,000 ¢ per kgm. wool is grown there).

Cattle are mainly Beef-breeds, be they stud (Angus, Charolais, M. Grey, Shorthorn or Hereford) or commercial crossbreds.

Goats are of both Angora and Cashmere types: no great numbers occur here yet, but numbers have been increasing steadily over the past decade.

In Zone 3:

Pinus radiata forests are increasingly being planted in place of the extensive natural eucalypt forests found in this highland area, (which is adjacent to the Blue Mountains and Warragamba Dam area).

Animal production here is similar to that found in Zone 2, but is more sparse: the Merino and goat populations are almost non-existent here.

Geology:

The District is mostly of basaltic origin, but granitic and shaley soils also occur in parts: there are at least 2 old volcanoes in the locality—one nearby (Mt. Canobolas —1295 m. A.S.L.); the other within the P.P.D. (Mt. Macquarie—1203 m. A.S.L.).

Soils in Zone 1 are mainly alluvials; Zone 2 has basaltic soils in its northern parts, and granitic in its southern. Zone 3 is basaltic in the main.

Watersheds:

Two water storages exist in the P.P.D., viz. Carcoar and Wyangala Dams.

Watersheds are easterly to the Macquarie River (Zone 3) and southerly and westerly to the Abercrombie and Lachlan Rivers (Zones 2 & 1). Springs occur widely on the farms of Zones 2 & 1. but there are no real marshes, (as in Macquarie Marshes).

Stock population:

(Average of Returns for seven years (1980—1986)).

* Range of numbers of stock 'returned'.

Division	Cattle	Sheep
A	34,741	353,690
	* (28,645 to 41,600)	(331,633 to 373,062)
B	27,899	314,265
	(22,222 to 35,244)	(272,490 to 353,640)
C	13,495	448,328
	(9,242 to 18,864)	(424,812 to 488,609)
D	10,553	248,494
	(7,445 to 14,930)	(236,924 to 256,985)

JOHNE'S DISEASE (OVINE):

Having painted a picture of the District, (which probably means more to those in Tableland Districts than to others), I will now turn to the disease.

Firstly, the location of affected properties is in a (40 km. diameter) small area south and south east of Blayney, covering parts of 'A', 'C' and 'D' Divisions. As I said previously. I suspect this is more the result of gradual discovery of the infection rather than by any 'epidemic' of disease-spread.

Secondly, the usual history and clinical picture is a small percentage of (usually) the older sheep show a protracted weight loss and wasting, without loss of appetite or fever or wool break (although wool may become 'tender'): their level of vitality gradually reduces as the wasting progresses: often they fail to respond to repeated endoparasitic therapy (fluke ± worm), even though scouring is not a regular feature — if it is, helminthosis could have arisen secondarily to the main problem.

The affected animals are usually home-breds, but I have seen cases in sheep introduced onto local properties, one from Yass P.P.D. sheep (off the property), the other from Bathurst P.P.D. sheep (from Saleyards).

The disease may not always 'present' in a typical way—I refer to the A.V.J. (1985) 62 (5): 171 report of mine, where the disease was diagnosed histopathologically from tissues forwarded for other clarifications, viz. liver disease, haemorrhagic enteritis.

I have enclosed a table in my notes of the 'statistics' relevant to each flock so far discovered: there is no breed specificity yet recognised.

Reference to textbook descriptions may help, when you meet your first case: Blood, Henderson, Radostits (p.643), Merck's Vet. Annual (p.319), and 'Animal Health in Australia' ip.165).

PATHOLOGY, HISTOPATHOLOGY, BACTERIOLOGY:

Precise details of J's. D. diagnosis can be found by reference to relevant standard texts. However I will quickly describe the main features of the disease as I have seen it, in its pathology, histopathology and bacteriology.

1. Pathology

General emaciation, loss of fat from depots. Serous or sero-fibrinous fluids in body cavities (result of hypoproteinaemia). Thickening of walls of terminal SI—rarely in proximal SI, sometimes in I/C valve, caecum and colon. Little macroscopic effect on intestinal mucosa except for coarse ridging or wrinkling in long standing cases.

Mesenteric lymph nodes (especially in ileo-caecal area) show 2—3 x enlargement, are moist (oedematous) when cut, but show no caseation, calcification or purulence.

Lymphangitis shows up as lymphatic cording sometimes is visible across ileal mesentery, between ileum and nearby lymph nodes.

2. Histopathology

Intestines:

Diffuse infiltration of intestinal mucosa and submucosa by oedema and infected epithelioid cells, lymphocytes and occasional eosinophils. Muscle layers are usually unaffected. Villi atrophise (sic) because of infiltration by infected cells, but do not become necrotic (as in Tuberculosis). No ulceration—so no loss of blood or mucus.

Lymph Nodes:

Become hyperplastic. Cortex contains focal epithelioid cell granulomas, (some with central. calcification). Medulla becomes oedematous, with many infected epithelioid cells and lymphocytes.

Lymphatics:

Focal lymphangitis present, with lumina blocked by cellular debris and infected cells.

3. Bacteriology

Ziehl-Nielsen positive organisms found in smears from intestinal mucosa, mesenteric lymph nodes; 'post-office box red'.

M. johnei is smaller than M. tuberculosis; occurs mainly as clumps in tissues. It is an obligate parasite and only grows at or near body-temperature (38°C): it only grows on special culture media, and 12 weeks incubation can be necessary.

There are 3 types of M. johnei: the classic one which affects cattle in most countries (including Australia), and two unusual ones in sheep from Iceland and Scotland (pigmented). The Australian Sheep one fits in, 'where I don't know'!!

The organism resists freezing and being in slurry for 287 days and in cattle manure for 11 months, but doesn't survive either in direct sunlight, in alkaline soils or when dried out.

THE FUTURE:

J's. D. is an insidious disease: it doesn't give rise to spectacular losses, but may exact deaths of 1-2% per year: in cattle the annual mortality apparently sometimes reaches 25%.

It is not only the deaths of clinically affected animals which are involved, but also the reduced productivity for the farmer caused by the wasting associated with the disease in 'in-contact, mildly-affected' animals: the possibility of neonatal infection, and of cross-species transference of this infection also need to be clarified in the future.

Trial work is being done in several local infected flocks, Departmental V.O's., V.R.O's., and F.A's., from the nearby R.V.L. and A.R. & V.C., (Orange) being involved in these exercises, as well as myself and the Ranger.

One study is to examine the effects on wool-production in a self-replacing Merino flock, over a sheep's productive lifetime: another is to study the mortalities in an infected Crossbred ewe flock, and others relate to correlating serology and disease-status in 'suspect' animals from infected farms which are forwarded to slaughter on consignment.

Departmental policy regarding quarantine in infected flocks has been examined; to date none is being imposed.

However, interstate-movement requirements may intrude here in the future, as may the increasing need to develop a specific serological test for 'live-animal' testing.

Vaccination (as practiced overseas) is another option which needs to be borne in mind, perhaps in individual flocks, as well as disease-control by the disposal of animals from infected farms before they become clinically ill but after they have contributed to the farmer's enterprise for several years.

CASE NO.	SHEEP NUMBERS				ENTERPRISE	ORIGIN	SHEEP CASES
	BREED	AT RISK	SICK	DEAD			FIRST	CURRENT	CATTLE
1. ARM	*De	140	?	6	S, F	H, C	1980	NO	55-
	-MXe, 1	410	-	-	F	H, S	-	-	&quo;
2. FID	*Dr	52	2	-	F	Flock 1	1982	-	NO
3. EHS	*Me, 1	2,500	20	40	W	H, S, C	1982	YES T1	290-
	-MXe,1	700	-	-	F	H, S, C	-	-	&quo;
4. MRV	*Xe,1	800	3	?	F	B, S	1982	YES T2	20-
5. MJH	*Mw	1,600	6	?	S, W	H, C	1982	NO	NO
6. IHW	Me/1	2,800	5%	?	S, W	H, S, C	1982	NO	150-
7. HJB	*Me, 1	2,000	4	1	W	H, S, C	1983	NO	150-
	-MXe, 1	700	-	-	F	H, S	-	-	&quo;
8. JRS	*Me, 1	1,200	2-3	1	W	H, S, C	1984	-	NO
9. KPW	*Mw	3,700	3	20+	W	B	1984	-?	NO
10. IOP	*Me, 1	1,600	6+	?	W	H, S	1985	YES T3	60-
11. PP	*Me, 1	1,500	3	2	W	H, S	1986	YES T3	?
12. GWC	*MXe, 1	1,200	?20	-	W, F	H, S	1987	YES ?T4	50-

LEGEND:

*	clinical cases in mob
D	Dorset
e	ewes
-	no clinical cases recognised
S	stud
H	home-bred replacements
M	Merino
l	lambs
F	fat lamb
S	irregular sire purchases
X	1st Xbd
w	wethers
W	wool cutters
C	closed flock
r	rams
B	bought-in regularly
T1 (2,3,4)	Trial Mob 1 (2,3,4)