Can rare mad cow disease spread to humans? Scientists tested on monkeys

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Volume 31, Number 5—May 2025

Dispatch

Administration of L-type Bovine Spongiform Encephalopathy to Macaques to Evaluate Zoonotic Potential

Abstract

We administered L-type bovine spongiform encephalopathy prions to macaques to determine their potential for transmission to humans. After 75 months, no clinical symptoms appeared, and prions were undetectable in any tissue by Western blot or immunohistochemistry. Protein misfolding cyclic amplification, however, revealed prions in the nerve and lymphoid tissues.

Conclusion

We noted no detectable evidence of PrPSc by WB or IHC in any tissues of L-BSE orally inoculated macaques. Nevertheless, PMCA successfully amplified PrPres from lymphatic and neural tissues. The PrPres exhibited electrophoretic patterns distinct from those detected by PMCA using L-BSE–affected cattle BH as the seed (Figure 3, panel C), indicating that the PrPSc used as the template for PrPres amplification in orally inoculated macaques did not originate from the bovine L-BSE prions used as inoculum. Instead, PrPSc were newly generated by the conversion of macaque PrPC by bovine L-BSE prions. Our results provide strong evidence that L-BSE can infect macaques via the oral route.

We found no evidence that PrPSc reached the brain in orally inoculated macaques; however, the macaques euthanized 6 years postinoculation might have been in the preclinical period. At low infection levels, lymph nodes play a vital role in prion spread to the central nervous system (11). Therefore, had the macaques been maintained for a longer period, they might have developed prion disease. Retrospective surveillance studies using the appendix and tonsil tissues suggested a considerable number of humans harboring vCJD in a carrier state (12). Thus, we cannot exclude that L-BSE orally inoculated macaques could similarly remain in a potentially infectious state.

The brain of L-BSE intracerebrally inoculated macaque accumulated prions with biochemical properties resembling bovine L-BSE prions (Figure 3, panel C; Appendix Figure 2); however, we observed no PrPSc accumulation in lymphoid tissues by WB or IHC (4). In contrast, macaques orally inoculated with C-BSE prions showed PrPSc accumulation in lymphoid tissues, including the spleen, tonsils, and mesenteric lymph nodes by WB and IHC (13). In our study, L-BSE orally inoculated macaques harbored C-BSE–like prions in their lymphoid and neural tissues. Interspecies transmission of L-BSE prions to ovine PrP transgenic mice can result in a shift toward C-BSE–like properties (14,15). Our data suggest that L-BSE prions may alter biophysical and biochemical properties, depending on interspecies transmission and inoculation route, acquiring traits similar to those of C-BSE prions. This transformation might result from structural changes in the L-BSE prion to C-BSE–like prions and other lymphotropic prions within lymphoid tissues or from the selective propagation of low-level lymphotropic substrains within the L-BSE prion population.

The first limitation of our study is that the oral inoculation experiment involved only 2 macaques and tissues collected at 6 years postinoculation, before disease onset. Consequently, subsequent progression of prion disease symptoms remains speculative. A larger sample size and extended observation periods are required to conclusively establish infection in orally inoculated macaques. Furthermore, we performed no bioassays for PMCA-positive samples, leaving the relationship between PMCA results and infectious titers undefined. Considering that PrPres amplifications from tissues from the orally inoculated macaque tissues required 2 rounds of PMCA, the PrPSc levels in positive tissues might have been extremely low and undetectable in the bioassay.

Snip…

Previous studies have demonstrated that L-BSE can be orally transmitted to cattle (7) and might have caused prion disease in farm-raised minks (6), indicating that L-BSE could naturally affect various animal species.

Our findings suggest that L-BSE can also be orally transmitted to macaques. Therefore, current control measures aimed at preventing primary C-BSE in cattle and humans may also need to consider the potential risk of spontaneous L-BSE transmission.

References…snip…end


***> Our results provide strong evidence that L-BSE can infect macaques via the oral route.

Wednesday, May 24, 2023

***> WAHIS, WOAH, OIE, United States of America Bovine spongiform encephalopathy Immediate notification




SATURDAY, MAY 20, 2023

***> Tennessee State Veterinarian Alerts Cattle Owners to Disease Detection Mad Cow atypical L-Type BSE



MAY 19, 2023


2 weeks before the announcement of this recent mad cow case in the USA, i submitted this to the APHIS et al;

***> APPRX. 2 weeks before the recent mad cow case was confirmed in the USA, in Tennessee, atypical L-Type BSE, I submitted this to the APHIS et al;

Document APHIS-2023-0027-0001 BSE Singeltary Comment Submission May 2, 2023

''said 'burden' cost, will be a heavy burden to bear, if we fail with Bovine Spongiform Encephalopathy BSE TSE Prion disease, that is why this information collection is so critical''...



TUESDAY, APRIL 15, 2025

Cases of Creutzfeldt-Jakob disease in young individuals: open questions regarding aetiology

Recently, two young individuals, aged 15 and 21, were diagnosed with sporadic Creutzfeldt-Jakob disease (sCJD) in Canada and the United States, respectively (D'Arcy et al., 2019; Ahn et al., 2024).



terry
 
Hey Terry - I'm reading this and here's what I took away from this...help me understand if I misunderstood (I'm terrible at science stuff)

Scientists gave a rare form of mad cow disease (L-type BSE) to monkeys to see if it could spread to humans. Turns out, it can cause brain damage similar to what's seen in humans with prion diseases. They also found it might be easier to transmit than the more common strain of BSE.

So yeah… that's a little unsettling.

Key takeaways:
  • L-type BSE might be more dangerous than we thought
  • It can cross species
  • Raising new questions about food safety and monitoring


So do you think this will impact how they test or regulate beef in the future?
 
Hey Terry - I'm reading this and here's what I took away from this...help me understand if I misunderstood (I'm terrible at science stuff)

Scientists gave a rare form of mad cow disease (L-type BSE) to monkeys to see if it could spread to humans. Turns out, it can cause brain damage similar to what's seen in humans with prion diseases. They also found it might be easier to transmit than the more common strain of BSE.

So yeah… that's a little unsettling.

Key takeaways:
  • L-type BSE might be more dangerous than we thought
  • It can cross species
  • Raising new questions about food safety and monitoring


So do you think this will impact how they test or regulate beef in the future?
No Sir, not here in the USA. The OIE et al have been concerned a bit with the atypical BSE in the last few years, because other transmission studies were very concerning, but still have not changed anything. With the USDA et al still testing <25k annually for BSE, that's just not much of a BSE Surveillance system, imo. Even with science showing atypical l-type BSE by oral transmission now to macaques, we now know atypical BSE transmits back to cattle by oral routes, add that to the fact the new scientific transmission studies with CWD, cattle, pigs, sheep, and Cervid, all orally infected by CWD, and the fact the Food and Drug Administration's BSE Feed Regulation (21 CFR 589.2000) feed ban does NOT Include elk and deer considered at high risk for CWD, the FDA recommends that these animals do not enter the animal feed system. However, this recommendation is guidance and not a requirement by law. Atypical BSE cases are now showing up more and more, more so than typical BSE. Maybe atypical BSE is not spontaneous? I believe that the BSE Feed Regulation (21 CFR 589.2000) Should be changed ASAP to inlude these changes in science. 300 NG is enough to transmit CWD to cervid by oral route. Cattle with the E211K polymorphism are susceptible to the CWD agent after oronasal exposure of 0.2 g of infectious material. …just my opinion…terry

Annex 7 (contd) AHG on BSE risk assessment and surveillance/March 2019

34 Scientific Commission/September 2019

3. Atypical BSE

The Group discussed and endorsed with minor revisions an overview of relevant literature on the risk of atypical BSE being recycled in a cattle population and its zoonotic potential that had been prepared ahead of the meeting by one expert from the Group. This overview is provided as Appendix IV and its main conclusions are outlined below. With regard to the risk of recycling of atypical BSE, recently published research confirmed that the L-type BSE prion (a type of atypical BSE prion) may be orally transmitted to calves1 . In light of this evidence, and the likelihood that atypical BSE could arise as a spontaneous disease in any country, albeit at a very low incidence, the Group was of the opinion that it would be reasonable to conclude that atypical BSE is potentially capable of being recycled in a cattle population if cattle were to be exposed to contaminated feed. Therefore, the recycling of atypical strains in cattle and broader ruminant populations should be avoided.

4. Definitions of meat-and-bone meal (MBM) and greaves


The L-type BSE prion is much more virulent in primates and in humanized mice than is the classical BSE prion, which suggests the possibility of zoonotic risk associated with the L-type BSE prion


Consumption of L-BSE–contaminated feed may pose a risk for oral transmission of the disease agent to cattle.


Thus, it is imperative to maintain measures that prevent the entry of tissues from cattle possibly infected with the agent of L-BSE into the food chain.


Atypical L-type bovine spongiform encephalopathy (L-BSE) transmission to cynomolgus macaques, a non-human primate

Fumiko Ono 1, Naomi Tase, Asuka Kurosawa, Akio Hiyaoka, Atsushi Ohyama, Yukio Tezuka, Naomi Wada, Yuko Sato, Minoru Tobiume, Ken'ichi Hagiwara, Yoshio Yamakawa, Keiji Terao, Tetsutaro Sata

Affiliations expand

PMID: 21266763

Abstract

A low molecular weight type of atypical bovine spongiform encephalopathy (L-BSE) was transmitted to two cynomolgus macaques by intracerebral inoculation of a brain homogenate of cattle with atypical BSE detected in Japan. They developed neurological signs and symptoms at 19 or 20 months post-inoculation and were euthanized 6 months after the onset of total paralysis. Both the incubation period and duration of the disease were shorter than those for experimental transmission of classical BSE (C-BSE) into macaques. Although the clinical manifestations, such as tremor, myoclonic jerking, and paralysis, were similar to those induced upon C-BSE transmission, no premonitory symptoms, such as hyperekplexia and depression, were evident. Most of the abnormal prion protein (PrP(Sc)) was confined to the tissues of the central nervous system, as determined by immunohistochemistry and Western blotting. The PrP(Sc) glycoform that accumulated in the monkey brain showed a similar profile to that of L-BSE and consistent with that in the cattle brain used as the inoculant. PrP(Sc) staining in the cerebral cortex showed a diffuse synaptic pattern by immunohistochemistry, whereas it accumulated as fine and coarse granules and/or small plaques in the cerebellar cortex and brain stem. Severe spongiosis spread widely in the cerebral cortex, whereas florid plaques, a hallmark of variant Creutzfeldt-Jakob disease in humans, were observed in macaques inoculated with C-BSE but not in those inoculated with L-BSE.


see full text;


''H-TYPE BSE AGENT IS TRANSMISSIBLE BY THE ORONASAL ROUTE''

This study demonstrates that the H-type BSE agent is transmissible by the oronasal route. These results reinforce the need for ongoing surveillance for classical and atypical BSE to minimize the risk of potentially infectious tissues entering the animal or human food chains.

 

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