1996-97 GLOBAL ANTHRAX REPORT
Presented at the Third Annual Conference on Anthrax, 7–11 September 1998, Plymouth, England

Martin Hugh-Jones, Department of Epidemiology & Community Health, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA

“Plus c’est la même chose, plus ça change.” During the past three decades, there has been a progressive global reduction in livestock cases in response to national programmes, however inept and clumsy they have been in many cases. And as each country takes on the challenge, reality is found to be different from the paradigm, sometimes better, frequently somewhat worse but not impossible. The commonest errors are to believe that systems that encourage incomplete recording and publication do little harm; similarly that using humans as sentinels is adequate to support cost-effective control procedures. Both beliefs are expensive and delay effective control. Anthrax is a disease for which effective control is much cheaper and for livestock eventually results in eradication — we have yet to discover how to economically control this disease in wildlife. For many parts of the world where this disease was a common scourge of livestock 90 years ago — USA & Canada, United Kingdom, northern Europe — it is now infrequent to rare, though maybe with an embarrassing persistence here and there to which we will later return. An increasing list of countries can truly claim freedom from it — Cyprus, New Zealand, Belize, the Caribbean with the exception of Haiti (and thus possibly the Dominican Republic), Malaysia, Taiwan, Sweden, Eire, and to which I am tempted to add Austria, Czech Republic, Denmark, Finland, Luxembourg, Malta, and the Guianas. But as we have exponentially improved our scientific knowledge of the pathogen, the ability to control the disease has lagged further and further behind.

In North America it has been most interesting. While the disease occurs sporadically in western Canada, where two recent cases were in herds not maintaining vaccination and had relaxed surveillance, it was seen again in Ontario after an apparent absence of some decades. There has been a recent outbreak in the Winnipeg Zoo involving three bison and a white-tailed deer; the cause is presently unknown. The situation in Wood Bison is fascinating in that after some vicious epidemics it is now in apparent abeyance. The sudden 1993 epidemic in the MacKenzie Bison Sanctuary, where it had never been seen before and then killed 10% of the bison, has been followed by an apparent total absence of disease. It is similarly quiet in the Wood Bison National Park in northern Alberta. A characteristic of the Wood Bison strain is that it produces no flux of blood from the carcass. This encourages the belief that death was due to other causes and, if nothing else, can significantly delay an accurate diagnosis when cattle are infected with it, for example in the two herds affected north of Edmonton and in the cattle grazing near Fort Vermilion. We have since come across this absence of perimortal bleeding in white-tailed deer in southwestern Texas and in cattle and goats in Kimberly, South Africa.

In the USA there have been sporadic cases in South Dakota, Nebraska, New Mexico, and Oklahoma; since 1991 there have been deaths in California, Kansas, Mississippi, and Arkansas. All appear to be possibly related to old anthrax graves. This summer (1998) there has been an outbreak in North Dakota, involving some six herds and 27 deaths in three separate areas, and well away from where it is usually noted. What triggered this is still unknown. In the summer of 1997 an epidemic declared itself in southwestern Texas affecting some 22 counties from Corpus Christie to the west of Del Rio. This uncovered a long lasting condition of hyperendemic anthrax in the area, primarily affecting white tailed deer and which overflowed into the adjoining livestock herds. Areas were affected which within living memory had never seen livestock anthrax. The deer herds were very severely afflicted, in some instances virtually wiped out, or so it is claimed. As with other wildlife epidemics this followed a “ten-year” cycle. In this case the spring rains had lasted unusually into the early summer and the epidemic spread was facilitated by the very large numbers of tabanid flies. Anecdotal evidence from individual deer ranchers indicate that white-tailed deer anthrax is blow fly dependent, as is kudu anthrax in the Kruger National Park; both deer species are browsers.

In the Caribbean the only country known to be affected is Haiti, where the US military is supervising a vaccination programme. The result has yet to be announced. As before, this presents an ongoing hazard to the Dominican Republic.

In Mexico and Central America the disease rages with slight effective controls and extensive under- recognition of the disease, especially in small ruminants. By our estimates it is hyperendemic in El Salvador and Guatemala; endemic in Mexico, Honduras, Nicaragua and Costa Rica. El Salvador continues to suffer a series of outbreaks in horses, which is unusual in itself and certainly in Central America. While it is presently absent from Belize, the increasing reports from there of problems with the veterinary service and a falling diagnostic laboratory quality would suggest that we might soon see infection crossing the border unopposed from Guatemala. While Panama claims to be without anthrax, private reliable information indicates it may in fact be sporadic in David.

In South America we have a number of countries that continue to claim to be free — the three Guianas [French Guiana, Guyana, and Suriname] and Colombia — and we have as yet no reason to formally doubt these claims. The disease is sporadic in Brazil, Ecuador, Paraguay, Uruguay, and Venezuela. Brazil, after many years of claiming to be unaffected, now reports that cases are sporadic in two states. Unfortunately, these clinical reports are not supported by laboratory confirmation. With inadequate veterinary cover in many Brazilian states and in the back country of others the reality could well be more severe and in line with their annual production of some ten million doses of vaccine, but it would still be “sporadic.” On the other hand, Uruguay has been involved an intensive vaccination and control programme that gives the onlooker confidence. For the rest, they are, at least, endemically afflicted, whatever their claims; Argentina and Bolivia provide no case or vaccination data while claiming successful reduction; Chile very extensively vaccinates each year, suggesting that any relaxation is associated with the immediate reappearance of the disease. Peru is deemed to be hyperendemically infected because of the high numbers of human cases; because it is only reported in cattle, which is clearly unlikely considering the significant numbers of sheep and goats even though many will be kept above 4,000m where the disease is known to not occur; and the severity of the outbreaks in 5/10 of the coastal provinces.

In Europe, the major afflicted regions continue to be Turkey and Greece. But regularly, significant numbers of outbreaks still occur in Spain, Albania, Italy (including Sicily and Sardinia), and Romania. Central Spain suffers a quite extraordinary number of human cases each year — from 152 in 1990 to 50 in 1996 — indicating a hyperendemic or even epidemic livestock situation. Only continuing peace will reveal the true situation in the Balkans. The reported incidence in Hungary is erratic but the vaccination level is high enough to indicate a probable endemic level. Elsewhere it is truly sporadic. The molecular epidemiology of B. anthracis strains from Norway indicates that it is importing contaminated livestock feed. As Norway is not part of the EU, its sources will not necessarily be common to the rest of Europe. While it has not been possible to indicate all its sources, the majority appear to be in southern Africa. Overall, it will be interesting to see in Europe what impact the current reaction to BSE will have by prohibiting the feeding of bovine meat and bone meal to cattle. Optimistically, we may expect the incidence to be reduced. The following countries would appear to be now “free”: Austria (though there is a modest level of ongoing vaccination), Czech Republic, Denmark, Finland, Latvia, Luxembourg, Malta, Northern Ireland, Sweden, quite apart from long term freedom in Cyprus, Ireland, and Iceland; Lithuania claims freedom but has too much vaccination to instil confidence.

In Russia, an outbreak involving one human death and eight people hospitalised from occupational exposure and enteric anthrax associated with dead cattle was reported southeast of Moscow in Tambov in 1995; in 1996 another outbreak, virtually identical, broke out in another village in the same general area, but this time with one death, 23 hospitalised, and 1,500 vaccinated. In 1996, a very similar outbreak with human and bovine cases was reported near Stavropol in southern Russia. In 1995, epidemiologically identical outbreaks had occurred in Tblisi, Georgia, and in and around Baku, Azerbaijan. Latterly there have been multiple human cases in Krasnodar and Stavropol, Kalnynya, and Sanatov. All these events reflect the poor quality of public health and veterinary services in their respective regions, an over-reliance on human sentinel cases, and on the economic pressure in the communities to buy and eat meat from dead and dying sick cattle.

The economic frailty of the federated countries of Central Asia must bode ill for the control of anthrax in that region, a northern part of the traditional Middle Eastern “anthrax belt.” Though reasonably controlled at the beginning of the decade, the number of human and livestock cases has increased rapidly in recent years. One of the problems in this region is the comparative weakness of the veterinary services and the parallel dependence on human vaccination by the medical profession, understandable in the face of the excessive numbers of human cases. . . for 1996, Azerbaijan (76), Kazakhstan (70 in five investigated outbreaks in first nine months), Kygyzstan (none reported in 1996 but 54 in the first 10 months of 1997), Tajikistan (105; 114 in 1997). The non recognition and reporting of livestock cases is the rule, not the exception. Presently there is a severe epidemic in southern Tajikistan and affecting the whole of the area.

Africa remains severely afflicted. West Africa is still the largest region in the world with hyperendemic and epidemic anthrax. This is reflection of the major civil unrest and collapse of effective veterinary controls in the region, as well as a climate — social, agricultural, ecological, and meteorological — fostering this disease. At the other end of the epidemiological spectrum are Malawi, which has claimed freedom for many years and a system of routine surveillance, and South Africa, which has gone from compulsory annual vaccination to voluntary vaccination. While the latter outbreak incidence is truly sporadic, it seems as if diagnosis sometimes gets delayed until significant deaths have occurred.

In Asia the success story is Indonesia where anthrax is now restricted to the provinces of East and West Nusatengarra; Indonesia was aided in this by Australia. A truly commendable event. However the widespread presence of porcine anthrax in the highlands of Papua New Guinea must make one suspect that the disease must persist in Irian Jaya. In the Philippines it is restricted to three provinces and essentially to Northern Luzon. The Republic of Korea, which had reported no cases between 1978 and 1994, suddenly had three outbreaks in 1994–95 but none since. India has undertaken to develop a national programme of anthrax control. They have mapped their cases and the disease is most common in the alkaline southeast of the country and decreasing in intensity as one goes northwest into the more acid soils, where it is rarely seen. The civil problems in Sri Lanka prevent laboratory confirmation of cases as the traditionally affected part of the country is in the Tamil north. In early 1997 Australia suffered a sudden and severe epidemic in northern Victoria, in an area with irrigated grazing and dairy farming that never had anthrax in over 80 years. Cases occurred on 79 farms, and some 47,600 cattle and 1,700 sheep were vaccinated in the Tatura area, an area of 25kms by 18kms. AFLP analysis showed that it was a strain from Tamil Nadu, probably and thus a survivor from historical outbreaks when contaminated bone meals had been imported from India. China has livestock anthrax throughout the country, but the eastern incidence is so low as to not generate human cases. The latter are found readily throughout the western mountainous parts of the country. There were 898 human cases reported in 1996 (5%CFR) and 1,210 (3%CFR) in 1997; livestock reported cases were 1570 (1996) and 1091 (1997). The livestock reports appear to be limited to cattle, never listing pigs (a commonly affected species in South East Asia), sheep (which would be expected in the west and north), and water buffalo (in the southern tier). Mongolia is severely affected in spite of extensive vaccination.

One cannot vaccinate forever. With surveillance, one can terminate vaccination after a limited period when the now susceptible stock become sentinels. But one must watch. Livestock vaccination should only be recontinued where new infections recur and only while they persist. There must be sufficient viable spores to initiate an infection, not just demonstrable spores in the soil. Unless there is a significant occupational risk, the vaccination of people is a public proof of the failure of a veterinary programme.

One of the epidemiological tragedies was Pasteur’s public “experiment” at Pouilly-le-Fort where the resulting massive sporulation instituted the belief in permanent ground contamination. This belief has too often prevented the thorough investigation of the sources of outbreaks. It is too easy to ascribe a case of anthrax to a previous death on the same farm in a previous decade, however distant, on the slimmest of evidence or even without any. The reality is that soil is dangerous for a limited period; many years ago Max Sterne defined it as “three months to three years.” Experience shows that he was correct. This is not to deny the existence of champs maudit and contaminated burial sites, but these are rare. If they were common, how did Cyprus successfully eradicate anthrax? Anthrax was long documented in Jamaica and in New Zealand where it has not been known in decades. Rain will concentrate spores in low laying areas to be consumed (grazed) in the following year, which reinforces the need for proper and adequate site control and disposal of infected carcasses. Scavenger animals and birds play an important part in many countries but how important? Not only must we investigate possible food borne outbreaks from recycled meat and bone meals or cross-contamination, there are also latent infections that later become lethal when the host animal (or human) is stressed. Thanks to our ability to “fingerprint” this pathogen and its conservative nature, we can now trace the geographic origins of outbreaks and feed contamination. The door is now open for new, exciting, and productive epidemiological investigations.