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This article was published in 1953
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Pleura-Pneumonia Contagiosa
D.G. CHRISTIE, B.V.Sc., H.D.A., District Veterinary Officer, ande.g. LOWE, B.V.Sc., Inspector of Stock, Coonamble
PART 2 - CENTRAL WEST
Since the method of control in this area was basically the same as in the Riverina—elimination of clinical cases, C.F. test, inoculation and quarantine of outbreak mobs for 90 days from last death; inoculation and similar quarantine of all contacts; and subsequent surveillance of outbreak cattle—no attempt will be made to repeat the detail of the routine handling of the various mobs. An endeavour will be made only to show the origin, so far as N.S.W. is concerned, of the series of outbreaks and distribution through the area; summarising finally to indicate the total involvement, and to stress any salient points which arose during the control.
Origin
All but 5 of the 29 outbreaks tie-up with 495 ex-Queensland cattle dispersed at the Gunnedah saleyards on 28th April, 1952; when some 1,200 grown cattle and 130 calves were offered. Of the 5 exceptions, one outbreak was related to those in the Riverina, the source of infection cannot be placed in three and in the fifth there is some evidence of a definite connection with the ex-Gunnedah cattle.
The first outbreak was reported in August, and occurred in New South Wales cattle sold at the Binnawav saleyards on 30th April. The infection was traced to contact with portion of a mob of ex-Gunnedah cattle which had been railed to Binnaway; the contact occurring across the fence of holding yards at the latter centre. This mixed mob was moved to Wellington and subsequently (on 23rd May and 4th July) dispersed from the saleyards there; causing ten (10) outbreaks in the Dubbo (4), Molong (2), Carcoar (2), Mudgee (1) and Bathurst (1) Districts; as well as in the area of the D.V.O. (South) (Riverina).
Spread Through the Central West
Gunnedah saleyards (28/4/52) —> Coonamble District.
Gunnedah saleyards (28/4/52) —> Coonabarabran District.
Gunnedah saleyards (28/4/52) —> Wagga saleyards.
Gunnedah saleyards (28/4/52) —> Binnaway saleyards.
Binnaway saleyards (30/4/53) —> Wellington saleyards (23/5/52 & 4/7/52) —> Dubbo. Molong. Carcoar. Mudgee and Bathurst Districts; and the Riverina.
OUTBREAKS
| District | No. of Outbreaks | No. of Cattle | Deaths and Destruction |
|---|---|---|---|
| Carcoar | 2 | 176 | 46 |
| Molong | 5 | 184 | 17 |
| Bathurst | 1 | 18 | 1 |
| Coonamble | 4 | 752 | 178 |
| Forbes | 4 | 572 | 38 |
| Dubbo | 5 | 462 | 106 |
| Mudgee | 2 | 368 | 4 |
| Coonabarabran | 6 | 1086 | 18 |
| Totals | 29 | 3618 | 408 |
PREVENTIVE INOCULATION
| District | No. of Holdings | No. of Cattle |
|---|---|---|
| Carcoar | 15 | 734 |
| Molong | 16 | 636 |
| Bathurst | 7 | 334 |
| Canonba | 3 | 65 |
| Coonamble | 9 | 853 |
| Forbes | 6 | 482 |
| Dubbo | 16 | 2295 |
| Mudgee | 5 | 137 |
| Coonabarabran | 50 | 3019 |
| Totals | 127 | 8555 |
Some particular features, and even peculiarities, connected with the distribution of the outbreaks might be instanced by the following:—
Coonamble. The first outbreak occurred about 21st September; showing an apparent incubation period of five (5) months, from the date of the Gunnedah sale. In this District early losses were complicated by the fact that at the time there was a prolific growth of trefoil and the first deaths were attributed to Hoven; a common experience in the area under such pasture conditions.
A Coonabarabran dealer (and/or his drover) proved to be a particular pest. In this case a mob ex Gunnedah walked the stock routes to the Coonamble District; and was responsible for the serious outbreak at Combara. Boxing and other contacts while loafing along the stock routes made action necessary on a large number of holdings. A considerable amount of work was involved in tracing mobs; the picture being complicated frequently by the fact that cattle from affected holdings were boxed with clean cattle, both on the holdings and, in case of drafts intended for sale, at the saleyards.
Bathurst. A local dealer purchased 98 head at the Wellington saleyards on 4/7/52; this total including 99 which had been running with some of the "contacts" from the Binnaway sale. Between the date of the Wellington sale and the diagnosis of the first outbreak (in August) the Bathurst mob had:— walked 9 miles from trucks to the new owner's property; walked back to Bathurst on 11/7/52 and through a special sale (760 head yarded); returned home, less 12 sold at the special. Then some 9 days later 34 head were sold privately and walked back over the 9 miles to trucks for movement to the Carcoar District.
The 12 head sold at Bathurst on 11th July were boxed with 103 head purchased at the same sale, and moved to a property 6 miles from Bathurst in another direction.
The balance of 12 head still with the Bathurst dealer when “the balloon went up" were inspected promptly; and found then to include one (1) clinical case. This was destroyed immediately, and the diagnosis confirmed post-mortem.
The subsequent inoculation and quarantine routine included all paddock contacts of either portion of the lot of 99 ex Wellington, and still in the Bathurst District, as well as cattle in an adjoining pen at the Bathurst sale. However, during the road movements described, these cattle could have made contact with those on any one of at least a dozen properties, including two dairies, en route; not to mention numerous suburban house cows.
The extraordinary fact, though, was that the net result comprised one only positive case; that being the one destroyed at the initial inspection of the residue of the consignment ex Wellington. Perhaps just to confirm the diagnosis, one further positive was found subsequently among the 34 head sold privately and moved to the Carcoar District.
CONTROL
As a genera] measure in this regard, bleeding and inoculation was carried out in all outbreaks at the outset. Bleeding was omitted later, because the outbreaks appeared to be fairly recent infections and reactors were showing up as clinical cases, often before the results were received from the laboratory.
SOME FEATURES
The C.F. Test. In one case a beast was sick for ten days before destruction. C.F. test was negative and the Director of Veterinary Research advised that specimens were Pleuro-positive. In a mob slaughtered at Orange, five showed definite sequestrum formation; and of these one was positive, one suspicious and the remainder negative to the C.F. test on bloods collected at the time of slaughter.
Incubation Period. In some cases the outbreaks were characterised by extremely long incubation periods. It is felt that in some of these showing unusually long periods the disease actually was quiescent and only became clinically obvious when predisposing conditions were favourable. In one instance a period of approximately 107 days occurred between infection and the first death. However, there is evidence to suggest that the particular mob was actively spreading infection between 23 and 65 days after being infected.
Importance of Frequent Inspections. This was borne out in an outbreak in the Coonamble District. 111 deaths and destructions occurred in a mob of 260. The mob was shot out on several occasions and any suspicious cases were checked carefully. On slaughter only three showed sequestrum formation in a total of 51.