Go Slow   -  What you need to know

The disease
After a successful hunt, you get home and feed your dogs some of the pig you caught. The next morning, the dogs are quieter than normal and as you head out on another hunt, some of them sit down and start trembling. Over the next couple of weeks, they seem fine in their kennels, but run out of energy on a short walk across the paddocks.

This is the typical story of Go Slow. Hunting dogs, farm dogs and pet dogs can all be affected, but most share a history of eating wild pig. All parts of the pig (meat, offal and bones) have been linked to cases, and cooking or freezing the pork does not make it safe to feed to dogs. Go Slow was first reported in Northland in the late 1990s, and a Northland pig hunting club newsletter mentions dogs suddenly losing energy and collapsing in 1992. The disease now occurs in most places throughout the North Island and in the last few years, Go Slow has been seen in several places where it was not previously recognized (including Gisborne, Taranaki and the Wairarapa). Go Slow does not seem to be a problem in the South Island, as there have been only two confirmed cases on a single farm in Canterbury since 2014.

Go Slow is a muscle disease in dogs linked to eating fresh, frozen or cooked wild pig. It causes dogs to lose energy and ‘run out of steam’ when exercising, and some dogs also tremble and collapse. Most recover with rest and there are some supplements that may help, but recovery can take months and some dogs never get back to full fitness and hunting. Go Slow seems to only occur in certain areas of the North Island. If it is present in your area, the easiest way to prevent your dogs from getting Go Slow is to not feed them wild pig or allow them to scavenge. The cause is currently unknown but is most likely a plant or fungal toxin that is eaten by pigs, and dogs are then exposed when they eat the pig. Further studies comparing the compounds in meat from normal and ‘Go Slow pigs’ are planned for later this year to try and figure out the cause, and this is where you can help.
Small samples (approximately 100 grams) of fresh or frozen meat (not cooked) from a wild pig that has been fed to dogs are needed for this study. Your dogs don’t have to have developed Go Slow to participate (although those cases are very useful too) as ‘normal’ wild pig samples are needed for comparison. If you’re interested in submitting a wild pig sample, or have any questions about Go Slow in general, please get in touch with Hayley Hunt at h.hunt@massey.ac.nz or call 027 3410874. Working together, hopefully we can add to what we know about Go Slow.

The Cause
Everything we have learnt about Go Slow so far suggests it is caused by a toxin in pig meat. It is not an infectious disease caused by a bacteria or virus so cannot be passed from dog to dog, although several dogs in a pack are often affected at once if they have eaten the same wild pig. The features of Go Slow (including where it occurs, the slow spread of cases down the North Island, and what the disease does to dogs’ muscles) fit best with it being caused by a toxin in a plant or fungus that is eaten by a pig, with dogs exposed to it through eating the pig. In pioneering days in the USA, there was a very similar disease called ‘The Slows’ or ‘Trembles’ that people developed after drinking milk from cows that had eaten a toxic plant, and we have some similar plants in NZ. However, looking for natural toxins is like looking for a needle in a haystack and there are no laboratory tests for most plant toxins, which makes researching the cause of Go Slow very difficult.

Pesticides including 1080, brodifacoum, cholecalciferol and cyanide have been investigated and ruled out as likely causes of Go Slow in dogs. Go Slow occurs in areas where there has been no use of these pesticides and the clinical, laboratory and muscle changes that we see with Go Slow do not fit with the way these chemicals work. Furthermore, the antidote for brodifacoum and cholecalciferol poisoning has been given to some dogs with Go Slow and did not improve their clinical signs, and a small number of pig and dog samples have been tested for 1080 with negative results.

Diagnosis and Treatment
The diagnosis of Go Slow may seem obvious if dogs have typical signs and have recently eaten wild pig, but not every case presents like this. Other diseases can cause lethargy and collapse, so do not assume that every dog that struggles on a hunt has Go Slow. An examination by a vet can help to rule out other diseases, and in some cases a simple blood test to measure muscle enzymes may be useful as Go Slow causes muscle damage.

If your dog is diagnosed with Go Slow, the most important thing you can do is rest the dog in a cage or small area, with no walks or hunting for a minimum of three weeks. Feed a high-quality diet and make sure lots of water is always available for the dog to drink. Go Slow affects the parts of the muscle cell that produce energy (mitochondria), so dogs will often seem normal in kennels and then show signs again during exercise. After three weeks, start with short walks and runs and slowly build up to hunting again. Complete recovery may take up to months to years in some cases, and unfortunately a small number of dogs never get back to their normal fitness or hunting ability. There is no vaccine or specific antidote for Go Slow. Dogs with severe signs may require in-clinic treatment at the vets, but in some mild to moderate cases the following supplements seem to help:
●    B vitamins, Vitamin E and selenium: There are supplements containing a mix of B vitamins, selenium and vitamin E specifically made for dogs, including Palamountains Exceed (a liquid that you add to food, which can be purchased from your vet or local farm store without a prescription). Vitamin B pills and powders can also be used, and a vitamin E/selenium injection can be given by your vet. Please note: selenium can be toxic in high doses, so the injectable form needs to be prescribed by a vet to ensure the correct dose is used.
●    Zentonil/Denosyl: This is a supplement designed to support liver function and aid in elimination of toxins (Go Slow is caused by an unknown toxin). This can be ordered through your vet without a prescription, but can be expensive (>$150 for 2 weeks for a 20kg dog).

Public Health
As well as the underlying cause, the other big question about Go Slow is whether people can get it, especially since freezing and cooking the meat does not prevent dogs from getting sick. In many cases of Go Slow in dogs, people have eaten the same meat and felt completely fine, suggesting people are not affected in the same way as dogs. However, a small number of hunters have said they had a sore stomach or felt like their heart was racing after eating pork that also made dogs sick, and there are members of the pig hunting community that have been diagnosed with chronic fatigue/fibromyalgia (which has no known cause and may be completely unrelated, but shares some similarities with Go Slow in dogs). Overall, the risk to people is probably very small and wild pork is an important food source for many hunters, so keep enjoying your wild pork roasts and sausages.
 
The exception to this is if your dog’s show any signs of Go Slow: any wild pig they ate in the 48 hours before developing signs should be thrown away (or sent for research, see below) and not eaten.

Additional info: the numbers behind the summary
●    86 cases were followed from 2014 – 2017. The patterns of cases identified in this study have continued from 2017-2020, although Go Slow is now more widespread than it was with cases more commonly seen in Gisborne and Taranaki (which was rare in 2017).
●    Of the 86 cases followed, 67% were in pig hunting dogs, 16% in pets and 14% in farm dogs.
●    Males and females equally affected (56% males, 44% females) In a survey of 203 normal pig hunting dogs, 55% were male
●    The ages of affected dogs from 6 months to 14 years
●    Pig dog lines containing heading dogs, cattle dogs, greyhounds, Labradors and bull terriers all seem to be affected equally, and Go Slow does not seem to be worse in some breeds than others. In farming situations, heading dogs often seemed to be worse affected than Huntaway’s, but this may just be due to their smaller body size (a smaller dog eating a similar amount of wild pig as a larger dog will get a larger dose of the toxin per kilo of their weight)
●    Cases of Go Slow are most common in June, and are rarely seen from Nov-March. This could be because of when hunting is most popular, or could mean that the Go Slow toxin is only present at certain times of the year
●    Of the 86 cases, 76 (88%) were known to have eaten wild pig in the week before developing Go Slow (usually in the 48hr before signs started). Another 8 dogs had either had the opportunity to scavenge or been missing in the bush, leaving only 2 cases with no obvious source of wild pig to eat.
●    68/86 dogs (79%) were lethargic/tired easily on hunts, 53 dogs (62%) had trembling or shaking and 29 dogs (34%) collapsed. Other signs of Go Slow included stiffness when walking (22 dogs), and sometimes vomiting and diarrhea (13-15 dogs)
●    Most dogs improved within 1-10 days, but many showed signs when they exercised again. Approximately 56% fully recovered within 2-3 months (back to fitness and hunting at the same level as prior to Go Slow), and many of the others recovered enough to hunt but were not back to full fitness. A small number of dogs were rehomed or euthanized as they could no longer hunt or work to the level required.
●    A whole pack may not show identical symptoms or effects, each dog may show individual symptoms.
●    Early signs of symptoms that are reported to a vet (24/48 hours), seem to be the most
effective and greater chance of recovery.
●    Seems to be more common in warmer climates in Native bush and not very prolific in Pine forests except where Native Bush is close by. But pigs can travel great distances and are unsure how long the toxin will stay in a pig's system for. 70/80% of cases from the upper third of the North Island.
●    No clear connection between the go slow toxin and areas used heavily in toxins i.e. 1080, brodifacoum, cholecalciferol, pindone etc. Low levels of brodifacoum were present in one sample of pork.
●    Zero cases of the toxin in domestic pigs, except in semi-wild / free range pigs that are able to enter Native bush.
●    Evidence suggests that the go slow toxin in pigs can’t be transferred to another pig, i.e. a sow can’t pass it to offspring, or through contact with a pig carrying the toxin. Evidence suggests it must be ingested by the individual animal.
●    Evidence suggests the same for dogs. That they can’t catch it from interaction with another dog or from pups suckling or through birth. Evidence suggests each dog must ingest the toxin in pork.
●    Evidence indicates that blood transfer from a dog stopping a pig is unlikely to transfer the toxin to a dog, and holding dogs are at a greater risk especially harder holding dogs.

The New Zealand Pig Hunting Association would like to thank Hayley Hunt and Jenni Petersen for all their hard work towards the treatment of dogs with go slow and the research that they have undertaken to combat this toxin and find out the best way to manage the best possible health of the dogs that are affected. For without their time and effort spent on investigating the cause of the go slow toxin and the treatments used and needed to keep our dogs alive and healthy, we would not be likely to beware of the dangers to our mates and the best way to care for them, which in turn would mean less pork in our freezers.

Thank you very much Hayley and Jenni for your time and dedication. Every Pig hunter will be very grateful for what you have done, and continue to do.