Thank you for the additional information on the kids.
As I noted before, there are a number of agents that can induce this neurologic disease complex that you have experienced with these kids. That said, when we see so many kids of different ages affected, our concerns are shifted a wee bit and we have to think about infectious disease, toxicities, and gross deficiencies. You did note a recent heavy rain, but the issues we might consider with this (ie liver fluke levels rising) wouldn't likely target the younger goats quite yet.
Now to note, your initial treatment approach was appropriate. While there are numerous agents that can induce these type of signs, it does sound like you did use a broad spectrum approach that would had addressed the majority of our concerns. That said, since treatment was obviously unsuccessful, it does raise our concerns to whether they were affected with an agent that wasn't being tackled by the treatment or whether the initiation of treatment was just too late to halt their decline.
In regards XXXXX XXXXX our probable differentials here, we need to first consider the infectious ones. If all the affected kids were grazing significantly, then that would open the floodgates to potential bacterial agents that could be our culprit. But since there were two very young kids, bacterial agents like Listeria would be lower on our list at the moment. As well, since we also had an older kid suffer with this condition, I would put issues like bacterial infections of the brain (Meningoencephalitis) lower on our list initially as well.
Now the reason why I asked about clostridial vaccination for this group is because that family of bacteria can cause a range of acutely fatal disease in both sheep and goats. They are also quite nasty and insidious, so despite the variety in ages of affected kids, they’d still be a consideration as a probable culprit. And while some are known to cause diarrhoea (as you noted was lacking), this is not always going to be seen. This is because some of the bacterial strains do not necessarily induce diarrhoea or we can see such severe subacute infections (my suspicion here) that the body doesn’t even have a chance to develop all of the clinical signs prior to death. Therefore, we’d still need to consider agents like C. perfringens Type C & D here even if we didn’t see overt GI signs of entertoxemia. Furthermore, to give us even more of a challenge, we do also have to consider that some strains of C. perfringens type D has been linked to potentially causing focal symmetrical encephalomalacia (which would give us the clinical signs you did see and could easily be mistaken for Vitamin B deficiency. And could explain why the Vitamin B shots had no effect). Furthermore, tetanus would be another clostridial disease to consider but it tends to cause rigid paralysis in the times between seizures (since any fit will have rigidity of the muscles during the period of fitting). So, it too could be a potential agent here.
Since two of the kids were under weaning age, this does make outright plant induced intoxication less of a concern (unless there is a particular toxic plant rife in the pasture that they may have had contact with). Just to note, in regards XXXXX XXXXX based toxins that could cause the severe neurological signs you have seen, we’d be thinking about any cyanogenic plants, Locoweed, Milkweed, or Ericaceae. Furthermore, and possibly more a risk with the varied age group, we can see these signs secondary to intoxication with lead, nitrites/nitrates (fertilizer), sodium monofluoroacetate, strychnine, ammonia, and organophosphates or organochlorines.
And just to briefly note the main nutritional issues that could appear in this manner, the most common tend to be thiamine (Vit B) deficiency, magnesium deficiency (again tends to be an issue for the weaned) and acute selenium toxicity (which you'd likely know if your supplementing this or if your land is heavy with it). With these signs, Vitamin B would have been the top suspect but obviously a lack of treatment response puts this one lower on the list (and perhaps raises clostridial suspicions).
So, as you can surely appreciate, there are quite a number of agents to consider for the demise of these wee one's. If we wanted to narrow our differential list further, especially since there are other animals potentially at risk, while it isn’t nice to think about, it would be worth considering submitting the recently dead kid for post mortem.It is getting a little bit on in age for getting bacterial samples (since after death the internal bacterial population can change and give us false appreciations of what was present at the time of death) but this would still be a valuable tool to rule out other causes here.
If you speak to the vet, they may be able to perform the autopsy in the practice. Alternatively, if you live near a vet school, agricultural college or veterinary lab, they will also be able to provide this service. The pathologist will be able to examine the internal organs for hints of which agent has induced this outbreak. If they cannot find an obvious gross cause of her death, they can collect samples to submit to the lab for the pathologists to evaluate.
The pathologists will be able to examine the tissues under the microscope and determine the causative agent that lead to her death. As well, if bacterial or viral causes are suspected, these can be cultured to determine what is present and what treatments will effectively clear them. And if necessary, they can also evaluate her parasite burden, check the GI for toxic plant/ heavy metal ingestion and check tissue mineral levels (to check for OD or deficiency). This will both give you closure on these sudden losses, but also help you know if this is something that threatens the whole group. And once you know the causative agent, you will be able to protect them effectively.
Therefore, in this situation, there are a number of differentials to consider. We can narrow down the differentials to what we have discussed on the history alone but to pinpoint the root cause, further steps need to be taken. And because we have to consider the rest of the herd here, an autopsy would be the most straightforward way to approach this situation and get some answers in identifying the culprit.
I hope this information is helpful.
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