20. African swine fever

African swine fever

African swine fever (ASF) is an acute highly fatal viral infection of pigs.  It is global in its distribution.  The disease reached PNG in 2020 after two pigs fed food waste from a Chinese construction camp kitchen near Mendi became ill and spread the disease to others.  From that point ASF spread along traditional trade routes through pig-to-pig contact, in meat scraps from infected pigs or following open kill in villages and free roaming pigs snuffling up blood or trim following a pig kill.

We knew from local information and NAQIA reports that the disease was in the area.  Senior staff were very cautious, and we kept a close watch on who came onto the site but a riot and mayhem in late November 2022 cast all our measures aside.  People connected to us were killed.  Our senior staff were withdrawn until security stabilised.  That meant there was no-one to actively control who came onto the site.  The construction crew working on site reported that many people came onto the farm to see the big white pigs.

Things weren’t going well on site.  Our building program had been seriously interrupted by the civil unrest and we fell months behind.  The buildings and pig farm site were supposed to be completed by September 2022, but the crew had not finished the fencing before the pigs arrived from Port Moresby in October.

Between October and November, the pigs grew very well (Figure1)  We had lost one sow from a gastric ulcer withing a month of arrival, probably associated with an injury during shipping that put her off feed and at risk.  Otherwise, the pigs settled in well and quickly adapted to their new home and the kau kau (sweet potato) silage.  While detection of oestrus was less than optimal from December after the riot, in November while the senior staff were present, we recorded nine sows as mated. 

Figure 1.Wonderland Agristock gilts November 2022

The security situation in Nogoli was such that it was unsafe for our senior staff to remain on site after the riot.  We kept a skeleton local crew to care for the pigs.  Staff managed the farm from a distance by Whats App.

Once compensation negotiations had concluded it was safe for staff to return.  However, on March 1, about a week before staff were due to return a sow was reported off feed and sick.  (Figure 2) 

She died the next day and the day after that two more sows were sick.  That history was enough to notify the chief veterinary officer (CVO) that ASF was suspected.  No other disease kills as quickly as ASF. 

Figure 2.  Staff member attending a sick sow.  March 2023 

The CVO thought we were overreacting, and that the disease was not ASF but anthrax, but not even anthrax kills that quickly.  Unfortunately, the NAQIA office in Tari had not been trained to use the rapid antigen test (RAT) kits for ASF.  Some NAQIA staff had been trained but the Tari man had missed out.  NAQIA offered to send staff from Port Moresby at our cost to do the testing but all I could see was delay.  The CVO did approve a rapid training session for one of our experienced senior staff at the NAQIA Kila Kila laboratory.  Murphy’s Law always applies, and we found ourselves trying to arrange all this late on the Friday of a long weekend. 

Our NGO, Business for Development, transferred operational funds to our man for local taxi expenses because NAQIA had no vehicles available.  Eventually our staff member arrived at the laboratory and was shown how to do the test.  We were lucky in a way that Covid had taught us about RATs so everyone was comfortable about using them.  NAQIA was running short of rapid antigen tests and could only spare four.  Our helpful NGO arranged travel to Tari on the Wednesday after the long weekend and our man arrived in Tari and then Nogoli that morning.  However, by the time he got to the farm on the 8^th March four more sows had died and six more died the next day.

Figure 3. Clinical signs of AFrican swine fever. Note the colour of the ears, snout and jowl.

 

Figure 4 Blood exuding from the snout 

Figure 5. Blood exuding from the anus

The RAT results were not very clear, but this is very much consistent with reports from veterinarians in the field.  One sow tested negative, but she was probably in the very early stage of infection because she died two days later.  A sow that miscarried was positive but again the result was not very clear.  A sick sow with blood extruding from the snout and anus was positive.  The fourth sow which was not eating, and which had skin redness around the neck and ears was positive.

Figure 6.  The ASF rapid antigen test. Note the pale line beneath the T denoting a positive result 

I was not at all happy with the quality of the test result.  We could not follow up because we had used up our four tests.  However, consultation with two laboratory diagnosticians skilled with ASF research and diagnostic tests confirmed our fears.  Significantly sows continued to die and by 10^th March, 18 sows and boars had died leaving only 8 still alive.  To try and contain the disease we shot any sick sows hoping to stop the disease before it could spread further.  Fat chance.  Three sows farrowed during the outbreak and died within a day of farrowing.  Their pigs died within 24 hours. This disease has never taken prisoners and by 16^th March, two weeks after the index case, our entire foundation herd of 24 sows and 3 boars was dead.

We buried all the dead pigs in a pit on the garden site about two hundred yards from the farm site.  They were covered with over a metre of soil.  It was quickly covered with vegetation within months.  We elected not to risk further local contamination by giving meat from the infected animals to local people.  Even though protein in the highlands is in short supply we thought the risk of the disease spreading in fresh meat was just too great. 

The source of infection was not identified but, because the disease was present in the area, it was linked to the significant numbers of undocumented visitors coming to the see the white pigs.

Figure 7. Cleaning the pens with soap and water

The buildings were thoroughly cleaned with soap and water and then disinfected (Figure 7) .  Quite frankly, soap and water, the local daily temperatures ofa tropical climate and time would kill any remaining virus.  Once we had completed construction on the site, made it secure and got the staff amenities building, with showers and a laundry finished we were ready to bring in new pigs.  We ran multiple training sessions with staff, bought a washing machine and multiple sets of overalls.  On June 26 2024, about 16 months after the outbreak, we introduced another group of gilts to be the foundation herd.  Our fingers are crossed.

A NAQIA officer said later that clearly our biosecurity wasn’t up to scratch and that taking pigs into Nogoli was a death sentence.  In a way he was right, but we didn’t expect to be farming in what turned out to be a war zone.  Nor did we expect that our fence was still not completed five months after the pigs arrived, also, the consequence of being in a war zone.  Try as we might, we couldn’t overcome the complexity of trying to keep our people safe, train staff, organise supply of construction and fencing materials and maintain a construction schedule in an environment where people feared getting shot or killed with a bush knife while going to work.