WEBVTT 1 00:00:04.170 --> 00:00:06.630 <v Instructor>Welcome to Module 2: Rabies.</v> 2 00:00:06.630 --> 00:00:08.550 Rabies is a very interesting disease 3 00:00:08.550 --> 00:00:12.330 because of its high case fatality rate, close to 100%. 4 00:00:12.330 --> 00:00:14.670 So it has a great impact on local 5 00:00:14.670 --> 00:00:16.260 and state health departments trying to deal 6 00:00:16.260 --> 00:00:18.210 with rabies exposures. 7 00:00:18.210 --> 00:00:19.980 And the healthcare cost to try 8 00:00:19.980 --> 00:00:22.803 to prevent human cases is high. 9 00:00:25.800 --> 00:00:27.600 So these are the topics that we're going 10 00:00:27.600 --> 00:00:30.663 to be covering in this slide presentation. 11 00:00:31.920 --> 00:00:34.710 And be sure when you review the slides 12 00:00:34.710 --> 00:00:36.720 that you look at the notes under each slide, 13 00:00:36.720 --> 00:00:39.210 where additional information is provided. 14 00:00:39.210 --> 00:00:41.670 So the rabies virus is an RNA virus 15 00:00:41.670 --> 00:00:45.060 in the Rahbdoviridae family, the Lyssavirus genus, 16 00:00:45.060 --> 00:00:47.490 is transmitted primarily through the saliva 17 00:00:47.490 --> 00:00:49.350 of infected animal. 18 00:00:49.350 --> 00:00:52.140 All mammals are susceptible to infection. 19 00:00:52.140 --> 00:00:54.390 There's been an occasional bird 20 00:00:54.390 --> 00:00:56.970 that had antibodies, indicating exposure, 21 00:00:56.970 --> 00:00:59.220 but apparently, the virus doesn't migrate 22 00:00:59.220 --> 00:01:00.480 to the brain in birds. 23 00:01:00.480 --> 00:01:03.210 So there's no clinical infections documented. 24 00:01:03.210 --> 00:01:05.220 It infects the central nervous system, 25 00:01:05.220 --> 00:01:09.150 and it's invariably fatal after the onset of clinical signs. 26 00:01:09.150 --> 00:01:12.453 This is a picture of the bullet-shaped rabies variant. 27 00:01:13.920 --> 00:01:15.390 In the United States, 28 00:01:15.390 --> 00:01:19.710 most of the US acquired cases are due to bats. 29 00:01:19.710 --> 00:01:21.720 And that's because bats have tiny teeth. 30 00:01:21.720 --> 00:01:25.110 And so people may not interpret that they were bitten. 31 00:01:25.110 --> 00:01:26.790 Or even if they realize they were bitten, 32 00:01:26.790 --> 00:01:29.040 the wound isn't bad enough to seek wound care. 33 00:01:29.040 --> 00:01:31.110 And so they're not thinking about rabies. 34 00:01:31.110 --> 00:01:34.140 There's about a handful, usually, on average, 35 00:01:34.140 --> 00:01:37.650 about three human cases reported annually in the US, 36 00:01:37.650 --> 00:01:39.540 and nearly all of them are fatal. 37 00:01:39.540 --> 00:01:43.350 Worldwide, a larger number of cases. 38 00:01:43.350 --> 00:01:47.070 59,000 to 70,000 per year estimated. 39 00:01:47.070 --> 00:01:49.860 And 99% of them are caused by dog bites 40 00:01:49.860 --> 00:01:53.400 and the dog variants outside the United States. 41 00:01:53.400 --> 00:01:57.540 This is the United States from 1928 to 2018. 42 00:01:57.540 --> 00:02:00.180 The solid line here is domestic animals 43 00:02:00.180 --> 00:02:02.670 and the dotted line are human cases. 44 00:02:02.670 --> 00:02:06.030 And you can see that the number of cases were high, 45 00:02:06.030 --> 00:02:08.640 you know, as high as 10,000 each year, 46 00:02:08.640 --> 00:02:11.730 in the United States through the 1940s, 47 00:02:11.730 --> 00:02:13.290 and then there was a mass vaccination 48 00:02:13.290 --> 00:02:16.110 of dogs against rabies, which was started in 1947. 49 00:02:16.110 --> 00:02:18.300 And you can see the number of cases dropping, 50 00:02:18.300 --> 00:02:20.313 both in domestic animals and humans. 51 00:02:21.810 --> 00:02:25.050 Worldwide, the green countries, like North America, 52 00:02:25.050 --> 00:02:27.930 do not have the dog variant of rabies. 53 00:02:27.930 --> 00:02:29.970 Now, dogs can occasionally still be infected 54 00:02:29.970 --> 00:02:31.170 by other variants, 55 00:02:31.170 --> 00:02:34.200 but at least we don't have the dog variant, 56 00:02:34.200 --> 00:02:36.750 which is so easy to be transmitted to people 57 00:02:36.750 --> 00:02:40.290 because how close dogs live in the human environment. 58 00:02:40.290 --> 00:02:42.030 The red countries are those 59 00:02:42.030 --> 00:02:45.480 that have dog-mediated human rabies, 60 00:02:45.480 --> 00:02:48.240 and the other countries are kind of in between 61 00:02:48.240 --> 00:02:52.410 in regards to perhaps not having human rabies, 62 00:02:52.410 --> 00:02:54.543 but the dog variant is present. 63 00:02:56.400 --> 00:02:57.870 The World Health Organization has 64 00:02:57.870 --> 00:02:59.670 three different categories of exposure. 65 00:02:59.670 --> 00:03:01.590 The United States does not. 66 00:03:01.590 --> 00:03:05.100 Just has either exposure or non-exposure. 67 00:03:05.100 --> 00:03:08.430 Be sure to look at the ACIP document on rabies 68 00:03:08.430 --> 00:03:10.230 to make this clear. 69 00:03:10.230 --> 00:03:12.240 Basically, in the United States, 70 00:03:12.240 --> 00:03:15.030 they tend to combine these category two or three exposures. 71 00:03:15.030 --> 00:03:16.920 So category one, no exposure, 72 00:03:16.920 --> 00:03:18.630 just touching or petting a rabid animal, 73 00:03:18.630 --> 00:03:20.280 feeding a rabid animal. 74 00:03:20.280 --> 00:03:22.380 Even licks from an animal 75 00:03:22.380 --> 00:03:26.100 that's shedding rabies virus in its saliva, 76 00:03:26.100 --> 00:03:27.630 if it's on intact skin, 77 00:03:27.630 --> 00:03:30.180 is not considered a rabies exposure. 78 00:03:30.180 --> 00:03:32.490 Category two is more mild exposures, 79 00:03:32.490 --> 00:03:36.090 where the rabid animal's nibbled uncovered skin, 80 00:03:36.090 --> 00:03:38.760 and there's minor scratches or abrasions without bleeding. 81 00:03:38.760 --> 00:03:43.530 And then definite bites or broken skin contact 82 00:03:43.530 --> 00:03:47.040 with the saliva of a rabid animal is a severe exposure. 83 00:03:47.040 --> 00:03:50.910 And any bat contact because of this issue of being bitten 84 00:03:50.910 --> 00:03:52.143 and not realizing it. 85 00:03:54.120 --> 00:03:55.050 Other transmission. 86 00:03:55.050 --> 00:03:57.450 There really is not good evidence 87 00:03:57.450 --> 00:04:00.870 for other routes of transmission. 88 00:04:00.870 --> 00:04:02.790 There have have been cases related 89 00:04:02.790 --> 00:04:05.190 to aerosolized virus in the laboratory. 90 00:04:05.190 --> 00:04:07.440 There was thought to be some cases related 91 00:04:07.440 --> 00:04:11.340 to inhalation of the virus in a bat cave, a small bat cave. 92 00:04:11.340 --> 00:04:13.950 But when they looked back at those cases further, 93 00:04:13.950 --> 00:04:17.730 they concluded it was likely due to bat bites. 94 00:04:17.730 --> 00:04:19.830 And there's no human-to-human transmission except 95 00:04:19.830 --> 00:04:22.593 for transplantation of infected tissues. 96 00:04:23.910 --> 00:04:25.170 Signs and symptoms. 97 00:04:25.170 --> 00:04:27.510 Highly variable incubation period. 98 00:04:27.510 --> 00:04:29.430 So the incubation period is the time period 99 00:04:29.430 --> 00:04:33.600 between when the person is exposed, or the animal exposed, 100 00:04:33.600 --> 00:04:35.460 and when they start showing symptoms. 101 00:04:35.460 --> 00:04:38.520 Usually one to three months. Varies by bite location. 102 00:04:38.520 --> 00:04:40.050 So if the bite is in the head, 103 00:04:40.050 --> 00:04:42.090 where the virus is closer to the brain, 104 00:04:42.090 --> 00:04:44.460 then it can be a shorter incubation period. 105 00:04:44.460 --> 00:04:47.130 The symptoms, non-specific prodrome, 106 00:04:47.130 --> 00:04:50.400 so fatigue, fever, and headache, are not specific. 107 00:04:50.400 --> 00:04:52.410 Could be all kinds of other diseases. 108 00:04:52.410 --> 00:04:54.930 But then it will progress to CNS symptoms 109 00:04:54.930 --> 00:04:58.680 because the viruses in the brain can either be furious 110 00:04:58.680 --> 00:05:00.870 or paralytic in humans or animals. 111 00:05:00.870 --> 00:05:02.460 And it can vary by species. 112 00:05:02.460 --> 00:05:03.900 For instance, cat species tend 113 00:05:03.900 --> 00:05:07.110 to be the more furious type of rabies, 114 00:05:07.110 --> 00:05:10.410 where they're attacking other animals and people, 115 00:05:10.410 --> 00:05:13.080 whereas dogs and raccoons may more often be just 116 00:05:13.080 --> 00:05:15.510 the paralytic, where they're not able to move. 117 00:05:15.510 --> 00:05:17.430 They're just stumbling around. 118 00:05:17.430 --> 00:05:21.000 The symptoms typically last anywhere from 2 to 10 days, 119 00:05:21.000 --> 00:05:22.863 ending then in coma and death. 120 00:05:24.120 --> 00:05:25.680 Diagnosis and testing. 121 00:05:25.680 --> 00:05:30.420 So before death, the saliva, 122 00:05:30.420 --> 00:05:34.380 skin biopsy, serum, and CFS can be tested 123 00:05:34.380 --> 00:05:36.030 in both animals and humans. 124 00:05:36.030 --> 00:05:38.820 However, there can be false negatives. 125 00:05:38.820 --> 00:05:40.950 So depending on how the test is done, 126 00:05:40.950 --> 00:05:44.490 the virus may be intermittently shedding in the saliva, 127 00:05:44.490 --> 00:05:45.630 there can be false negatives. 128 00:05:45.630 --> 00:05:50.160 So you really need to follow up with confirmatory tests 129 00:05:50.160 --> 00:05:52.800 on the brainstem and cerebellum postmortem. 130 00:05:52.800 --> 00:05:55.890 We cannot rely on the accuracy of antimortem tests 131 00:05:55.890 --> 00:05:57.780 to determine if an animal is rabid, 132 00:05:57.780 --> 00:06:00.960 because we wanna know with 100% certainty 133 00:06:00.960 --> 00:06:03.720 whether the person who was bitten needs rabies treatment. 134 00:06:03.720 --> 00:06:08.720 And so that's why confirmatory tests require euthanasia. 135 00:06:08.970 --> 00:06:13.970 Now, there are ways to determine in certain species, 136 00:06:14.370 --> 00:06:17.400 like dogs and cats, where it's been determined 137 00:06:17.400 --> 00:06:22.110 that if they have rabies virus in their saliva, 138 00:06:22.110 --> 00:06:25.170 they can't survive more than 10 days. 139 00:06:25.170 --> 00:06:30.170 And so you can confine a dog or cat after a bite, 140 00:06:30.300 --> 00:06:31.833 and if it stays healthy for 10 days, 141 00:06:31.833 --> 00:06:33.840 then you know that it wasn't rabid, 142 00:06:33.840 --> 00:06:36.600 at least at the time of the bite. 143 00:06:36.600 --> 00:06:39.030 But otherwise, antimortem testing doesn't help you 144 00:06:39.030 --> 00:06:42.180 with dogs and cats that have bitten somebody. 145 00:06:42.180 --> 00:06:45.330 Okay, treatment. There's no antiviral treatment. 146 00:06:45.330 --> 00:06:48.390 There is post-exposure prophylaxis, or PEP, 147 00:06:48.390 --> 00:06:50.700 that's administered as a series of four to five doses 148 00:06:50.700 --> 00:06:52.683 as soon as possible after exposure. 149 00:06:54.263 --> 00:06:55.096 So first of all, 150 00:06:55.096 --> 00:06:57.690 the most important thing is to wash thoroughly the wound. 151 00:06:57.690 --> 00:07:00.990 And then if the post-exposure vaccine is given, 152 00:07:00.990 --> 00:07:02.700 it can help fight off the virus 153 00:07:02.700 --> 00:07:05.370 and prevent it from migrating up to the brain. 154 00:07:05.370 --> 00:07:06.780 Another important component 155 00:07:06.780 --> 00:07:10.260 is human rabies immune globulin, HRIG. 156 00:07:10.260 --> 00:07:12.690 And that is given in the wound. 157 00:07:12.690 --> 00:07:15.720 And again, it's fighting off the virus in the wound 158 00:07:15.720 --> 00:07:18.060 and preventing it from going up to the brain. 159 00:07:18.060 --> 00:07:19.500 About 60,000 people 160 00:07:19.500 --> 00:07:22.650 in the US receive PEP each year due to exposure, 161 00:07:22.650 --> 00:07:25.620 and it's nearly 100% effective 162 00:07:25.620 --> 00:07:28.860 if it's given properly, with immunoglobulin, 163 00:07:28.860 --> 00:07:30.213 and given in time. 164 00:07:31.260 --> 00:07:32.400 So prevention. 165 00:07:32.400 --> 00:07:35.490 PrEP, pre-exposure prophylaxis, 166 00:07:35.490 --> 00:07:38.820 for high-risk individuals like veterinarians, 167 00:07:38.820 --> 00:07:42.453 animal control officers, people working with wildlife. 168 00:07:44.370 --> 00:07:46.680 So that's an injection, a vaccine. 169 00:07:46.680 --> 00:07:49.710 You can also distribute wildlife rabies vaccine bait. 170 00:07:49.710 --> 00:07:51.720 And that's what's pictured here with a quarter 171 00:07:51.720 --> 00:07:53.520 to show the size of them. 172 00:07:53.520 --> 00:07:55.140 There've been different formulations of baits, 173 00:07:55.140 --> 00:07:56.880 but these are the ones being used now. 174 00:07:56.880 --> 00:07:59.040 So there's a liquid vaccine inside. 175 00:07:59.040 --> 00:08:01.590 This is often a fish meal polymer 176 00:08:01.590 --> 00:08:04.560 or some other kind of polymer that smells good, 177 00:08:04.560 --> 00:08:06.690 particularly to raccoons, and tastes good. 178 00:08:06.690 --> 00:08:10.470 And these are distributed by hand in a city, 179 00:08:10.470 --> 00:08:13.140 where you toss them behind dumpsters or in bushes, 180 00:08:13.140 --> 00:08:15.420 anywhere where you think raccoons might be hanging out. 181 00:08:15.420 --> 00:08:16.830 And when they eat these, 182 00:08:16.830 --> 00:08:18.750 they get vaccinated through the mouth. 183 00:08:18.750 --> 00:08:21.600 You can also distribute these by plain or by helicopter 184 00:08:21.600 --> 00:08:24.720 in more rural or mountainous areas. 185 00:08:24.720 --> 00:08:27.360 There is approved vaccine for dogs, cats, ferrets, 186 00:08:27.360 --> 00:08:28.470 horses, cattle, and sheep. 187 00:08:28.470 --> 00:08:31.263 You can see a picture here of a dog being injected. 188 00:08:32.400 --> 00:08:34.650 Raccoons, if they're caught in traps, 189 00:08:34.650 --> 00:08:39.600 can also receive a parenteral injection as well. 190 00:08:39.600 --> 00:08:41.310 But often you're catching the raccoons 191 00:08:41.310 --> 00:08:43.650 in traps afterwards to draw blood 192 00:08:43.650 --> 00:08:45.720 in order to see if they have antibodies 193 00:08:45.720 --> 00:08:48.660 to determine whether your bait campaign worked. 194 00:08:48.660 --> 00:08:50.670 There are dog import regulations 195 00:08:50.670 --> 00:08:53.400 to prevent dog variant rabies from being imported 196 00:08:53.400 --> 00:08:54.870 into the United States. 197 00:08:54.870 --> 00:08:56.070 Often there's a conflict, 198 00:08:56.070 --> 00:08:57.990 particularly with service people overseas, 199 00:08:57.990 --> 00:09:01.440 who adopt wild dogs and make them into pets 200 00:09:01.440 --> 00:09:02.790 while they're overseas, 201 00:09:02.790 --> 00:09:05.370 and then they want to bring them back to the United States. 202 00:09:05.370 --> 00:09:06.750 And so there are regulations 203 00:09:06.750 --> 00:09:10.080 to try to prevent dog rabies 204 00:09:10.080 --> 00:09:11.820 from being imported into the United States, 205 00:09:11.820 --> 00:09:14.553 but occasionally it still comes through that way. 206 00:09:15.390 --> 00:09:17.040 Okay, animal reservoirs. 207 00:09:17.040 --> 00:09:19.710 The rabies virus is adapted to specific animal hosts 208 00:09:19.710 --> 00:09:21.540 in different geographic areas. 209 00:09:21.540 --> 00:09:26.160 And if the virus is adapted to the primary animal host, 210 00:09:26.160 --> 00:09:30.150 often that animal will not show symptoms right away 211 00:09:30.150 --> 00:09:33.360 or for a period of time. 212 00:09:33.360 --> 00:09:37.080 And in 2022, in the United States, 213 00:09:37.080 --> 00:09:40.140 most reported animal rabies cases were in bats. 214 00:09:40.140 --> 00:09:44.100 And bat rabies is worldwide. And in raccoons. 215 00:09:44.100 --> 00:09:48.540 And cats represent the most domestic animal rabies cases. 216 00:09:48.540 --> 00:09:52.290 They tend to not be vaccinated quite as well as dogs. 217 00:09:52.290 --> 00:09:56.250 The US was declared canine rabies variant free in 2007, 218 00:09:56.250 --> 00:09:58.560 but dogs can still be infected with other variants. 219 00:09:58.560 --> 00:10:00.900 And I'll show you a picture in a minute of the variants 220 00:10:00.900 --> 00:10:03.450 that we have in the United States. 221 00:10:03.450 --> 00:10:05.160 Okay, so here's the picture. 222 00:10:05.160 --> 00:10:07.980 And you can study this more at your leisure. 223 00:10:07.980 --> 00:10:09.540 FX stands for fox. 224 00:10:09.540 --> 00:10:14.540 So we have the Arctic fox variant up here in Alaska. 225 00:10:14.550 --> 00:10:17.550 We've had fox variant at different times 226 00:10:17.550 --> 00:10:19.470 down in the continental United States. 227 00:10:19.470 --> 00:10:22.710 Currently we have a fox variant in Arizona. 228 00:10:22.710 --> 00:10:25.380 The green area is a raccoon variant. 229 00:10:25.380 --> 00:10:27.930 And the raccoon variant keeps trying to spread north. 230 00:10:27.930 --> 00:10:30.210 In fact, there have been some cases 231 00:10:30.210 --> 00:10:32.910 in the Canadian provinces bordering here, 232 00:10:32.910 --> 00:10:34.710 Quebec and Ontario. 233 00:10:34.710 --> 00:10:36.750 It's trying to spread west. 234 00:10:36.750 --> 00:10:38.310 That's particularly why we do 235 00:10:38.310 --> 00:10:42.120 those vaccine baiting campaigns for raccoons, 236 00:10:42.120 --> 00:10:45.600 is because once a geographic area gets raccoon variants, 237 00:10:45.600 --> 00:10:50.600 the number of animal rabies cases skyrocket, 238 00:10:50.670 --> 00:10:54.300 because raccoons interact when they're rabid 239 00:10:54.300 --> 00:10:57.960 with a lot of other wild and domestic species. 240 00:10:57.960 --> 00:11:00.900 And then you have increased exposures to people 241 00:11:00.900 --> 00:11:02.700 whenever you have the raccoon variant. 242 00:11:02.700 --> 00:11:04.230 We've got some skunk variants here 243 00:11:04.230 --> 00:11:05.753 in the central part of the United States. 244 00:11:06.870 --> 00:11:09.900 And remember, the bat variant is not depicted here. 245 00:11:09.900 --> 00:11:10.733 It's throughout. 246 00:11:12.210 --> 00:11:14.010 Okay, the impact of climate change. 247 00:11:14.010 --> 00:11:15.810 This is just one example. 248 00:11:15.810 --> 00:11:17.580 The common vampire bat is one 249 00:11:17.580 --> 00:11:19.500 of the main wildlife species responsible 250 00:11:19.500 --> 00:11:22.170 for transmitting rabies to domestic animals, 251 00:11:22.170 --> 00:11:25.200 dogs and livestock, and humans in Latin America. 252 00:11:25.200 --> 00:11:26.310 In Latin America, 253 00:11:26.310 --> 00:11:28.350 in places where they don't have window screens, 254 00:11:28.350 --> 00:11:30.780 the vampire bats will come fly in at night 255 00:11:30.780 --> 00:11:33.360 while people are sleeping and feed on their toes, 256 00:11:33.360 --> 00:11:35.310 and the people will get rabies that way. 257 00:11:35.310 --> 00:11:37.650 They'll also feed on cattle, 258 00:11:37.650 --> 00:11:40.500 flying in to feed on the cattle legs. 259 00:11:40.500 --> 00:11:44.070 So as the time has been passing, 260 00:11:44.070 --> 00:11:49.070 you find that the range of the vampire bats is moving north. 261 00:11:50.400 --> 00:11:52.800 And in fact, that range is expected to extend 262 00:11:52.800 --> 00:11:56.340 into the continental United States within 27 years. 263 00:11:56.340 --> 00:11:59.310 So that would be really problematic, 264 00:11:59.310 --> 00:12:01.320 if we end up with vampire bat rabies 265 00:12:01.320 --> 00:12:03.720 in the continental United States. 266 00:12:03.720 --> 00:12:06.180 This last slide has some links 267 00:12:06.180 --> 00:12:08.550 that are important for you to check out. 268 00:12:08.550 --> 00:12:11.580 And I hope you enjoy learning more 269 00:12:11.580 --> 00:12:14.553 about this complex and fascinating disease.